assignment statements in ruby

Expressions

Operator expressions, miscellaneous expressions, command expansion, backquotes are soft, parallel assignment, nested assignments, other forms of assignment, conditional execution, boolean expressions, defined, and, or, and not, if and unless expressions, if and unless modifiers, case expressions, break, redo, and next, variable scope and loops.

Ruby 2.7 Reference SAVE UKRAINE

In Ruby, assignment uses the = (equals sign) character. This example assigns the number five to the local variable v :

Assignment creates a local variable if the variable was not previously referenced.

Abbreviated Assignment

You can mix several of the operators and assignment. To add 1 to an object you can write:

This is equivalent to:

You can use the following operators this way: + , - , * , / , % , ** , & , | , ^ , << , >>

There are also ||= and &&= . The former makes an assignment if the value was nil or false while the latter makes an assignment if the value was not nil or false .

Here is an example:

Note that these two operators behave more like a || a = 0 than a = a || 0 .

Multiple Assignment

You can assign multiple values on the right-hand side to multiple variables:

In the following sections any place “variable” is used an assignment method, instance, class or global will also work:

You can use multiple assignment to swap two values in-place:

If you have more values on the right hand side of the assignment than variables on the left hand side, the extra values are ignored:

You can use * to gather extra values on the right-hand side of the assignment.

The * can appear anywhere on the left-hand side:

But you may only use one * in an assignment.

Array Decomposition

Like Array decomposition in method arguments you can decompose an Array during assignment using parenthesis:

You can decompose an Array as part of a larger multiple assignment:

Since each decomposition is considered its own multiple assignment you can use * to gather arguments in the decomposition:

Conditionals

if statements allow you to take different actions depending on which conditions are met. For example:

• if the city is equal to ( == ) "Toronto" , then set drinking_age to 19.
• Otherwise ( else ) set drinking_age to 21.

true and false

Ruby has a notion of true and false. This is best illustrated through some example. Start irb and type the following:

The if statements evaluates whether the expression (e.g. ' city == "Toronto" ) is true or false and acts accordingly.

Most common conditionals

Here is a list of some of the most common conditionals:

String comparisons

How do these operators behave with strings? Well, == is string equality and > and friends are determined by ASCIIbetical order.

What is ASCIIbetical order? The ASCII character table contains all the characters in the keyboard. It lists them in this order:

Start irb and type these in:

elsif allows you to add more than one condition. Take this for example:

Let's go through this:

• If age is 60 or more, we give a senior fare.
• If that's not true, but age is 14 or more, we give the adult fare.
• If that's not true, but age is more than 2 we give the child fare.
• Otherwise we ride free.

Ruby goes through this sequence of conditions one by one. The first condition to hold gets executed. You can put as many elsif 's as you like.

Example - fare_finder.rb

To make things more clear, let's put this in a program. The program asks for your age and gives you the corresponding fare.

Type this in and run it. It should behave like this:

This will output:

Here age is both greater than 10 and greater than 20. Only the first statement that holds true gets executed.

The correct way to write this would be:

Re-arrange these characters in ASCIIbetical order:

The ASCII table contains all the characters in the keyboard. Use irb to find out wheter the characters "?" lies:

• After 9 but before A.
• After Z but before a.

Using your experience the previous question, make a program that accepts a character input and tells you if the character lines:

Then try the program with the following characters:

Sample answers:

• $ lies before 0
• < lies between 9 and A
• - lies between Z and a
• ~ lies after z

The Ruby Programming Language by David Flanagan, Yukihiro Matsumoto

Get full access to The Ruby Programming Language and 60K+ other titles, with a free 10-day trial of O'Reilly.

There are also live events, courses curated by job role, and more.

Assignments

An assignment expression specifies one or more values for one or more lvalues. lvalue is the term for something that can appear on the lefthand side of an assignment operator. (Values on the righthand side of an assignment operator are sometimes called rvalues by contrast.) Variables, constants, attributes, and array elements are lvalues in Ruby. The rules for and the meaning of assignment expressions are somewhat different for different kinds of lvalues, and each kind is described in detail in this section.

There are three different forms of assignment expressions in Ruby. Simple assignment involves one lvalue, the = operator, and one rvalue. For example:

Abbreviated assignment is a shorthand expression that updates the value of a variable by applying some other operation (such as addition) to the current value of the variable. Abbreviated assignment uses assignment operators like += and *= that combine binary operators with an equals sign:

Finally, parallel assignment is any assignment expression that has more than one lvalue or more than one rvalue. Here is a simple example:

Parallel assignment is more complicated when the number of lvalues is not the same as the number of rvalues or when there is an array on the right. Complete details follow.

The value of an assignment expression is the value (or an array of the values) assigned. Also, the assignment operator is “right-associative”—if multiple assignments appear in a single expression, they are evaluated from right to left. This means that the assignment can be chained to assign the same value to multiple variables:

Note that this is not a case of parallel assignment—it is two simple assignments, chained together: y is assigned the value 0 , and then x is assigned the value (also 0 ) of that first assignment.

Assignment and Side Effects

More important than the value of an assignment expression is the fact that assignments set the value of a variable (or other lvalue) and thereby affect program state. This effect on program state is called a side effect of the assignment.

Many expressions have no side effects and do not affect program state. They are idempotent . This means that the expression may be evaluated over and over again and will return the same value each time. And it means that evaluating the expression has no effect on the value of other expressions. Here are some expressions without side effects:

It is important to understand that assignments are not idempotent:

Some methods, such as Math.sqrt , are idempotent: they can be invoked without side effects. Other methods are not, and this largely depends on whether those methods perform assignments to nonlocal variables.

Assigning to Variables

When we think of assignment, we usually think of variables, and indeed, these are the most common lvalues in assignment expressions. Recall that Ruby has four kinds of variables: local variables, global variables, instance variables, and class variables. These are distinguished from each other by the first character in the variable name. Assignment works the same for all four kinds of variables, so we do not need to distinguish between the types of variables here.

Keep in mind that the instance variables of Ruby’s objects are never visible outside of the object, and variable names are never qualified with an object name. Consider this assignment:

The lvalues in this expression are not variables; they are attributes, and are explained shortly.

Assignment to a variable works as you would expect: the variable is simply set to the specified value. The only wrinkle has to do with variable declaration and an ambiguity between local variable names and method names. Ruby has no syntax to explicitly declare a variable: variables simply come into existence when they are assigned. Also, local variable names and method names look the same—there is no prefix like $ to distinguish them. Thus, a simple expression such as x could refer to a local variable named x or a method of self named x . To resolve this ambiguity, Ruby treats an identifier as a local variable if it has seen any previous assignment to the variable. It does this even if that assignment was never executed. The following code demonstrates:

Assigning to Constants

Constants are different from variables in an obvious way: their values are intended to remain constant throughout the execution of a program. Therefore, there are some special rules for assignment to constants:

Assignment to a constant that already exists causes Ruby to issue a warning. Ruby does execute the assignment, however, which means that constants are not really constant.

Assignment to constants is not allowed within the body of a method. Ruby assumes that methods are intended to be invoked more than once; if you could assign to a constant in a method, that method would issue warnings on every invocation after the first. So, this is simply not allowed.

Unlike variables, constants do not come into existence until the Ruby interpreter actually executes the assignment expression. A nonevaluated expression like the following does not create a constant:

Note that this means a constant is never in an uninitialized state. If a constant exists, then it has a value assigned to it. A constant will only have the value nil if that is actually the value it was given.

Assigning to Attributes and Array Elements

Assignment to an attribute or array element is actually Ruby shorthand for method invocation. Suppose an object o has a method named m= : the method name has an equals sign as its last character. Then o.m can be used as an lvalue in an assignment expression. Suppose, furthermore, that the value v is assigned:

The Ruby interpreter converts this assignment to the following method invocation:

That is, it passes the value v to the method m= . That method can do whatever it wants with the value. Typically, it will check that the value is of the desired type and within the desired range, and it will then store it in an instance variable of the object. Methods like m= are usually accompanied by a method m , which simply returns the value most recently passed to m= . We say that m= is a setter method and m is a getter method. When an object has this pair of methods, we say that it has an attribute m . Attributes are sometimes called “properties” in other languages. We’ll learn more about attributes in Ruby in Accessors and Attributes .

Assigning values to array elements is also done by method invocation. If an object o defines a method named []= (the method name is just those three punctuation characters) that expects two arguments, then the expression o[x] = y is actually executed as:

If an object has a []= method that expects three arguments, then it can be indexed with two values between the square brackets. The following two expressions are equivalent in this case:

Abbreviated Assignment

Abbreviated assignment is a form of assignment that combines assignment with some other operation. It is used most commonly to increment variables:

+= is not a real Ruby operator, and the expression above is simply an abbreviation for:

Abbreviated assignment cannot be combined with parallel assignment: it only works when there is a single lvalue on the left and a single value on the right. It should not be used when the lvalue is a constant because it will reassign the constant and cause a warning. Abbreviated assignment can, however, be used when the lvalue is an attribute. The following two expressions are equivalent:

Abbreviated assignment even works when the lvalue is an array element. These two expressions are equivalent:

Note that this code uses -= instead of += . As you might expect, the -= pseudooperator subtracts its rvalue from its lvalue.

In addition to += and -= , there are 11 other pseudooperators that can be used for abbreviated assignment. They are listed in Table 4-1 . Note that these are not true operators themselves, they are simply shorthand for expressions that use other operators. The meanings of those other operators are described in detail later in this chapter. Also, as we’ll see later, many of these other operators are defined as methods. If a class defines a method named + , for example, then that changes the meaning of abbreviated assignment with += for all instances of that class.

Table 4-1. Abbreviated assignment pseudooperators

The ||= Idiom

As noted at the beginning of this section, the most common use of abbreviated assignment is to increment a variable with += . Variables are also commonly decremented with -= . The other pseudooperators are much less commonly used. One idiom is worth knowing about, however. Suppose you are writing a method that computes some values, appends them to an array, and returns the array. You want to allow the user to specify the array that the results should be appended to. But if the user does not specify the array, you want to create a new, empty array. You might use this line:

Think about this for a moment. It expands to:

If you know the || operator from other languages, or if you’ve read ahead to learn about || in Ruby, then you know that the righthand side of this assignment evaluates to the value of results , unless that is nil or false . In that case, it evaluates to a new, empty array. This means that the abbreviated assignment shown here leaves results unchanged, unless it is nil or false , in which case it assigns a new array.

The abbreviated assignment operator ||= actually behaves slightly differently than the expansion shown here. If the lvalue of ||= is not nil or false , no assignment is actually performed. If the lvalue is an attribute or array element, the setter method that performs assignment is not invoked.

Parallel Assignment

Parallel assignment is any assignment expression that has more than one lvalue, more than one rvalue, or both. Multiple lvalues and multiple rvalues are separated from each other with commas. lvalues and rvalues may be prefixed with * , which is sometimes called the splat operator , though it is not a true operator. The meaning of * is explained later in this section.

Most parallel assignment expressions are straightforward, and it is obvious what they mean. There are some complicated cases, however, and the following subsections explain all the possibilities.

Same number of lvalues and rvalues

Parallel assignment is at its simplest when there are the same number of lvalues and rvalues:

In this case, the first rvalue is assigned to the first lvalue; the second rvalue is assigned to the second lvalue; and so on.

These assignments are effectively performed in parallel, not sequentially. For example, the following two lines are not the same:

One lvalue, multiple rvalues

When there is a single lvalue and more than one rvalue, Ruby creates an array to hold the rvalues and assigns that array to the lvalue:

You can place an * before the lvalue without changing the meaning or the return value of this assignment.

If you want to prevent the multiple rvalues from being combined into a single array, follow the lvalue with a comma. Even with no lvalue after that comma, this makes Ruby behave as if there were multiple lvalues:

Multiple lvalues, single array rvalue

When there are multiple lvalues and only a single rvalue, Ruby attempts to expand the rvalue into a list of values to assign. If the rvalue is an array, Ruby expands the array so that each element becomes its own rvalue. If the rvalue is not an array but implements a to_ary method, Ruby invokes that method and then expands the array it returns:

The parallel assignment has been transformed so that there are multiple lvalues and zero (if the expanded array was empty) or more rvalues. If the number of lvalues and rvalues are the same, then assignment occurs as described earlier in Same number of lvalues and rvalues . If the numbers are different, then assignment occurs as described next in Different numbers of lvalues and rvalues .

We can use the trailing-comma trick described above to transform an ordinary nonparallel assignment into a parallel assignment that automatically unpacks an array on the right:

Different numbers of lvalues and rvalues

If there are more lvalues than rvalues, and no splat operator is involved, then the first rvalue is assigned to the first lvalue, the second rvalue is assigned to the second lvalue, and so on, until all the rvalues have been assigned. Next, each of the remaining lvalues is assigned nil , overwriting any existing value for that lvalue:

If there are more rvalues than lvalues, and no splat operator is involved, then rvalues are assigned—in order—to each of the lvalues, and the remaining rvalues are discarded:

The splat operator

When an rvalue is preceded by an asterisk, it means that that value is an array (or an array-like object) and that its elements should each be rvalues. The array elements replace the array in the original rvalue list, and assignment proceeds as described above:

In Ruby 1.8, a splat may only appear before the last rvalue in an assignment. In Ruby 1.9, the list of rvalues in a parallel assignment may have any number of splats, and they may appear at any position in the list. It is not legal, however, in either version of the language, to attempt a “double splat” on a nested array:

Array, range and hash rvalues can be splatted. In general, any rvalue that defines a to_a method can be prefixed with a splat. Any Enumerable object, including enumerators (see Enumerators ) can be splatted, for example. When a splat is applied to an object that does not define a to_a method, no expansion is performed and the splat evaluates to the object itself.

When an lvalue is preceded by an asterisk, it means that all extra rvalues should be placed into an array and assigned to this lvalue. The value assigned to that lvalue is always an array, and it may have zero, one, or more elements:

In Ruby 1.8, a splat may only precede the last lvalue in the list. In Ruby 1.9, the lefthand side of a parallel assignment may include one splat operator, but it may appear at any position in the list:

Note that splats may appear on both sides of a parallel assignment expression:

Finally, recall that earlier we described two simple cases of parallel assignment in which there is a single lvalue or a single rvalue. Note that both of these cases behave as if there is a splat before the single lvalue or rvalue. Explicitly including a splat in these cases has no additional effect.

Parentheses in parallel assignment

One of the least-understood features of parallel assignment is that the lefthand side can use parentheses for “subassignment.” If a group of two or more lvalues is enclosed in parentheses, then it is initially treated as a single lvalue. Once the corresponding rvalue has been determined, the rules of parallel assignment are applied recursively—that rvalue is assigned to the group of lvalues that was in parentheses. Consider the following assignment:

This is effectively two assignments executed at the same time:

But note that the second assignment is itself a parallel assignment. Because we used parentheses on the lefthand side, a recursive parallel assignment is performed. In order for it to work, b must be a splattable object such as an array or enumerator.

Here are some concrete examples that should make this clearer. Note that parentheses on the left act to “unpack” one level of nested array on the right:

The value of parallel assignment

The return value of a parallel assignment expression is the array of rvalues (after being augmented by any splat operators).

Parallel Assignment and Method Invocation

As an aside, note that if a parallel assignment is prefixed with the name of a method, the Ruby interpreter will interpret the commas as method argument separators rather than as lvalue and rvalue separators. If you want to test the return value of a parallel assignment, you might write the following code to print it out:

This doesn’t do what you want, however; Ruby thinks you’re invoking the puts method with three arguments: x , y=1 , and 2 . Next, you might try putting the parallel assignment within parentheses for grouping:

This doesn’t work, either; the parentheses are interpreted as part of the method invocation (though Ruby complains about the space between the method name and the opening parenthesis). To actually accomplish what you want, you must use nested parentheses:

This is one of those strange corner cases in the Ruby grammar that comes as part of the expressiveness of the grammar. Fortunately, the need for syntax like this rarely arises.

Get The Ruby Programming Language now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.

Don’t leave empty-handed

Get Mark Richards’s Software Architecture Patterns ebook to better understand how to design components—and how they should interact.

It’s yours, free.

Check it out now on O’Reilly

Dive in for free with a 10-day trial of the O’Reilly learning platform—then explore all the other resources our members count on to build skills and solve problems every day.

Ruby Assignments in Conditional Expressions

For around two and a half years, I had been working in a Python 2.x environment at my old job . Since switching companies, Ruby and Rails has replaced Python and Flask. At first glance, the languages don’t seem super different, but there are definitely common Ruby idioms that I needed to learn.

While adding a new feature, I came across code that looked like this:

Intuitively, I guessed this meant “if some_func() returns something, do_something with it.” What took a second was understanding that you could do an assignment conditional expressions.

Coming from Python

In Python 2.x land (and any Python 3 before 3.8), assigning a variable in a conditional expression would return a syntax error:

Most likely, the assignment in a conditional expression is a typo where the programmer meant to do a comparison == instead.

This kind of typo is a big enough issue that there is a programming style called Yoda Conditionals , where the constant portion of a comparison is put on the left side of the operator. This would cause a syntax error if = were used instead of == , like this:

Back to Ruby

Now that I’ve come across this kind of assignment in Ruby for the first time, I searched whether assignments in conditional expressions were good style. Sure enough, the Ruby Style Guide has a section called “Safe Assignment in Condition” . The section and examples are short and straightforward. You should take a look if this Ruby idiom is new to you!

What is interesting about this idiom is that the assignment should be wrapped in parentheses. Take a look at the examples from the Ruby Style Guide:

Why is the first example bad? Well, the Style Guide also says that you shouldn’t put parentheses around conditional expressions . Parentheses around assignments in conditional expressions are specifically called out as an exception to this rule.

My guess is that by enforcing two different conventions, one for pure conditionals and one for assignments in conditionals, the onus is now on the programmer to decide what they want to do. This should prevent typos where an assignment = is used when a comparison == was intended, or vice versa.

The Python Equivalent

As called out above, assignments in conditional expressions are possible in Python 3.8 via PEP 572 . Instead of using an = for these kinds of assignments, the PEP introduced a new operator := . As parentheses are more common in Python expressions, introducing a new operator := (informally known as “the walrus operator”!!) was probably Python’s solution to the typo issue.

Ruby's case statement - advanced techniques

Nothing could be simpler and more boring than the case statement. It’s a holdover from C. You use it to replace a bunch of ifs. Case closed. Or is it? Actually, case statements in Ruby are a lot richer and more complex than you might imagine. Let’s take a look.

• Jul 15, 2015

Nothing could be simpler and more boring than the case statement. It's a holdover from C. You use it to replace a bunch of ifs. Case closed. Or is it?

Actually, case statements in Ruby are a lot richer and more complex than you might imagine. Let's take a look at just one example:

This example shows that case statements not only match an item's  value but also its  class . This is possible because under the hood, Ruby uses the === operator, aka. the three equals operator.

A quick tour of the === operator

When you write x === y y in Ruby, you're asking "does y belong in the group represented by x?" This is a very general statement. The specifics vary, depending on the kind of group you're working with.

Strings, regular expressions and ranges all define their own ===(item) methods, which behave more or less like you'd expect.  You can even add a triple equals method to your own classes.

Now that we know this, we can do all sorts of tricks with case.

Matching ranges in case statements

You can use ranges in case statements thanks to the fact that range === n simply returns the value of range.include?(n) . How can I be so sure? It's in the docs .

Matching regular expressions with case statements

Using regexes in  case statements is also possible, because /regexp/ === "string" returns true only if the string matches the regular expression. The docs for Regexp explain this.

Matching procs and lambdas

This is kind of a weird one. When you use   Proc#===(item) , it's the same as doing Proc#call(item) . Here are the docs  for it. What this means is that you can use lambdas and procs in your case statement as dynamic matchers.

Writing your own matcher classes

As I mentioned above, adding custom case behavior to your classes is as simple as defining your own === method. One use for this might be to pull out complex conditional logic into multiple small classes. I've sketched out how that might work in the example below:

• Try Honeybadger for FREE Honeybadger helps you find and fix errors before your users can even report them. Get set up in minutes and check monitoring off your to-do list. Start free trial Easy 5-minute setup — No credit card required
• Get the Honeybadger newsletter Each month we share news, best practices, and stories from the DevOps & monitoring community—exclusively for developers like you. Sign up Include latest Ruby articles

Starr Horne

Starr Horne is a Rubyist and Chief JavaScripter at Honeybadger.io. When she's not neck-deep in other people's bugs, she enjoys making furniture with traditional hand-tools, reading history and brewing beer in her garage in Seattle.

• @starrhorne Author Twitter

More Ruby articles

• Apr 09, 2024 Account-based subdomains in Rails
• Mar 12, 2024 Let's build a Hanami app
• Mar 05, 2024 How to deploy a Rails app to Render
• Feb 12, 2024 Visualizing Ahoy analytics in Rails
• Feb 07, 2024 Building reusable UI components in Rails with ViewComponent
• Jan 17, 2024 Composite primary keys in Rails
• Dec 14, 2023 Deploy a Rails app to a VPS with Kamal
• Nov 20, 2023 How to build your own user authentication system in Rails
• Nov 02, 2023 How to organize your code using Rails Concerns
• Oct 16, 2023 FactoryBot for Rails testing

Try the only application health monitoring tool that allows you to track application errors, uptime, and cron jobs in one simple platform.

• Know when critical errors occur, and which customers are affected.
• Respond instantly when your systems go down.
• Improve the health of your systems over time.
• Fix problems before your customers can report them!

As developers ourselves, we hated wasting time tracking down errors—so we built the system we always wanted.

Honeybadger tracks everything you need and nothing you don't, creating one simple solution to keep your application running and error free so you can do what you do best—release new code. Try it free and see for yourself.

Honeybadger is trusted by top companies like:

Get Honeybadger's best Ruby articles in your inbox

We publish 1-2 times per month. Subscribe to get our Ruby articles as soon as we publish them.

We're Honeybadger. We'll never send you spam; we will send you cool stuff like exclusive content, memes, and swag.

Using the Case (Switch) Ruby Statement

GrapchicStock / Getty Images

• Ruby Programming
• PHP Programming
• Java Programming
• Javascript Programming
• Delphi Programming
• C & C++ Programming
• Visual Basic

In most computer languages , the case or conditional (also known as  switch ) statement compares the value of a variable with that of several constants or literals and executes the first path with a matching case. In Ruby , it's a bit more flexible (and powerful).

Instead of a simple equality test being performed, the case equality operator is used, opening the door to many new uses.

There are some differences from other languages though. In C , a switch statement is a kind of replacement for a series of if and goto statements. The cases are technically labels, and the switch statement will go to the matching label. This exhibits a behavior called "fallthrough," as the execution doesn't stop when it reaches another label.

This is usually avoided using a break statement, but fallthrough is sometimes intentional. The case statement in Ruby, on the other hand, can be seen as a shorthand for a series of if statements. There is no fallthrough, only the first matching case will be executed.

The Basic Form of a Case Statement

The basic form of a case statement is as follows.

As you can see, this is structured something like an if/else if/else conditional statement. The name (which we'll call the value ), in this case inputted from the keyboard, is compared to each of the cases from the when clauses (i.e.  cases ), and the first when block with a matching case will be executed. If none of them match, the else block will be executed.

What's interesting here is how the value is compared to each of the cases. As mentioned above, in C++ , and other C-like languages, a simple value comparison is used. In Ruby, the case equality operator is used.

Remember that the type of the left-hand side of a case equality operator is important, and the cases are always the left-hand side. So, for each when clause, Ruby will evaluate case === value until it finds a match.

If we were to input Bob , Ruby would first evaluate "Alice" === "Bob" , which would be false since String#=== is defined as the comparison of the strings. Next, /[qrz].+/i === "Bob" would be executed, which is false since Bob doesn't begin with Q, R or Z.

Since none of the cases matched, Ruby will then execute the else clause.

How the Type Comes Into Play

A common use of the case statement is to determine the type of value and do something different depending on its type. Though this breaks Ruby's customary duck typing, it's sometimes necessary to get things done.

This works by using the Class#=== (technically, the Module#=== ) operator, which tests if the right-hand side is_a? left-hand side.

The syntax is simple and elegant:

Another Possible Form

If the value is omitted, the case statement works a bit differently: it works almost exactly like an if/else if/else statement. The advantages of using the case statement over an ​ if statement, in this case, are merely cosmetic.

A More Compact Syntax

There are times when there are a large number of small when clauses. Such a case statement easily grows too large to fit on the screen. When this is the case (no pun intended), you can use the then keyword to put the body of the when clause on the same line.

While this makes for some very dense code, as long as each when clause is very similar, it actually becomes more readable.

When you should use single-line and multi-line when clauses are up to you, it's a matter of style. However, mixing the two is not recommended - a case statement should follow a pattern to be as readable as possible.

Case Assignment

Like if statements, case statements evaluate to the last statement in the when clause. In other words, they can be used in assignments to provide a kind of table. However, don't forget that case statements are much more powerful than simple array or hash lookups. Such a table doesn't necessarily need to use literals in the when clauses.

If there is no matching when clause and no else clause, then the case statement will evaluate to nil .

• What Are Ternary (Conditional) Operators in Ruby?
• How to Use String Substitution in Ruby
• Java Expressions Introduced
• Using the Switch Statement for Multiple Choices in Java
• An Abbreviated JavaScript If Statement
• JavaScript Nested IF/ELSE Statements
• Using the "Split" Method
• Creating Two Dimensional Arrays in Ruby
• Control Statements in C++
• Basic Guide to Creating Arrays in Ruby
• Using the Command Line to Run Ruby Scripts
• Using the Each Method in Ruby
• Global Variables in Ruby

• Trending Now
• Foundational Courses
• Data Science
• Practice Problem
• Machine Learning
• System Design
• DevOps Tutorial
• Ruby Programming Language
• Ruby For Beginners
• Ruby Programming Language (Introduction)
• Comparison of Java with other programming languages
• Similarities and Differences between Ruby and C language
• Similarities and Differences between Ruby and C++
• Environment Setup in Ruby
• How to install Ruby on Linux?
• How to install Ruby on Windows?
• Interesting facts about Ruby Programming Language
• Ruby | Keywords
• Ruby | Data Types
• Ruby Basic Syntax
• Hello World in Ruby
• Ruby | Types of Variables
• Global Variable in Ruby
• Comments in Ruby
• Ruby | Ranges
• Ruby Literals
• Ruby Directories
• Ruby | Operators
• Operator Precedence in Ruby
• Operator Overloading in Ruby
• Ruby | Pre-define Variables & Constants
• Ruby | unless Statement and unless Modifier

Control Statements

• Ruby | Decision Making (if, if-else, if-else-if, ternary) | Set - 1
• Ruby | Loops (for, while, do..while, until)

Ruby | Case Statement

• Ruby | Control Flow Alteration
• Ruby Break and Next Statement
• Ruby redo and retry Statement
• BEGIN and END Blocks In Ruby
• File Handling in Ruby
• Ruby | Methods
• Method Visibility in Ruby
• Recursion in Ruby
• Ruby Hook Methods
• Ruby | Range Class Methods
• The Initialize Method in Ruby
• Ruby | Method overriding
• Ruby Date and Time

OOP Concepts

• Object-Oriented Programming in Ruby | Set 1
• Object Oriented Programming in Ruby | Set-2
• Ruby | Class & Object
• Private Classes in Ruby
• Freezing Objects | Ruby
• Ruby | Inheritance
• Polymorphism in Ruby
• Ruby | Constructors
• Ruby | Access Control
• Ruby | Encapsulation
• Ruby Mixins
• Instance Variables in Ruby
• Data Abstraction in Ruby
• Ruby Static Members
• Ruby | Exceptions
• Ruby | Exception handling
• Catch and Throw Exception In Ruby
• Raising Exceptions in Ruby
• Ruby | Exception Handling in Threads | Set - 1
• Ruby | Exception Class and its Methods
• Ruby | Regular Expressions
• Ruby Search and Replace

Ruby Classes

• Ruby | Float Class
• Ruby | Integer Class
• Ruby | Symbol Class
• Ruby | Struct Class
• Ruby | Dir Class and its methods
• Ruby | MatchData Class

Ruby Module

• Ruby | Module
• Ruby | Comparable Module
• Ruby | Math Module
• Include v/s Extend in Ruby

Collections

• Ruby | Arrays
• Ruby | String Basics
• Ruby | String Interpolation
• Ruby | Hashes Basics
• Ruby | Hash Class
• Ruby | Blocks

Ruby Threading

• Ruby | Introduction to Multi-threading
• Ruby | Thread Class-Public Class Methods
• Ruby | Thread Life Cycle & Its States

Miscellaneous

• Ruby | Types of Iterators
• Ruby getters and setters Method

The case statement is a multiway branch statement just like a switch statement in other languages. It provides an easy way to forward execution to different parts of code based on the value of the expression.

There are 3 important keywords which are used in the case statement:

• case : It is similar to the switch keyword in another programming languages. It takes the variables that will be used by when keyword.
• when : It is similar to the case keyword in another programming languages. It is used to match a single condition. There can be multiple when statements into a single case statement.
• else : It is similar to the default keyword in another programming languages. It is optional and will execute when nothing matches.

Flow Chart:

Important Points:

Please Login to comment...

Similar reads.

• Ruby-Basics
• 5 Reasons to Start Using Claude 3 Instead of ChatGPT
• 6 Ways to Identify Who an Unknown Caller
• 10 Best Lavender AI Alternatives and Competitors 2024
• The 7 Best AI Tools for Programmers to Streamline Development in 2024
• 30 OOPs Interview Questions and Answers (2024)

Improve your Coding Skills with Practice

What kind of Experience do you want to share?

How To Use When In Ruby: Essential Tips For Effective Coding

In this article, we delve into Ruby's 'when' keyword, a pivotal element in crafting concise case statements. Tailored for developers, we'll dissect its syntax, practical applications, and best practices, enhancing your Ruby coding efficiency.

Ruby, a language admired for its elegance and readability, offers a unique feature in its 'when' syntax, a component of case statements. This article explores the nuances of using 'when' in Ruby, providing clarity on its functionality and practical applications. By understanding this aspect, you can write more efficient and readable code, enhancing your Ruby programming skills.

Understanding The 'When' Syntax In Ruby

Basic structure of a case statement, implementing 'when' in conditional logic, best practices for using 'when', common mistakes and how to avoid them, real-world examples of 'when' in action, frequently asked questions, example with simple conditions, using ranges, multiple conditions.

The 'when' syntax in Ruby is a crucial part of the case statement , a control structure similar to switch statements in other languages. It provides a cleaner and more readable way to test a sequence of conditions.

Here's a simple example to illustrate:

Ranges can also be used effectively with 'when'. This is particularly useful for scenarios like score ranges.

'When' can handle multiple conditions in a single line, enhancing the flexibility of case statements.

By understanding these aspects of the 'when' syntax, Ruby programmers can write more concise and readable conditional logic. This syntax not only simplifies the code but also makes it more maintainable and less prone to errors.

The Case Keyword

Adding when conditions, the else clause, complete example.

The case statement in Ruby serves as a multi-way conditional, similar to if/elsif/else constructs but often more concise and readable. It's particularly useful for comparing a variable against multiple values.

A case statement begins with the case keyword, followed by the variable you're evaluating. This sets up the context for the subsequent when conditions.

Each when keyword introduces a new condition to compare against the variable. If the condition matches, the corresponding block of code is executed.

An else clause can be included to handle any cases not covered by the when conditions. This acts as a default or fallback.

Here's a complete example using a case statement:

Understanding the basic structure of a case statement is key to utilizing this elegant and efficient conditional tool in Ruby. It simplifies complex conditional logic and enhances the readability of the code.

Matching Single Conditions

Matching multiple conditions, using ranges in 'when', combining 'when' with other ruby features.

In Ruby, the 'when' clause is a powerful tool for implementing conditional logic . It allows for clear and concise expression of multiple conditions within a case statement.

A basic use of 'when' is to match a single condition. This is straightforward and similar to an 'if' statement but is more readable when you have multiple conditions.

'When' can also match multiple conditions in a single line, which is useful for grouping similar cases.

Ranges are elegantly handled in 'when' clauses, allowing for intuitive range-based conditions.

'When' clauses can be combined with other Ruby features like methods or regex for more complex conditions.

By incorporating 'when' into your Ruby code, you can handle complex conditional logic in a more organized and readable manner. This enhances the maintainability and clarity of your code, especially when dealing with multiple conditions.

Keep Conditions Simple

Use ranges judiciously, avoid overusing 'when', combine conditions when possible, default with 'else'.

Using 'when' in Ruby not only simplifies your code but also makes it more readable. However, to maximize its effectiveness, certain best practices should be followed.

Simplicity is key. Each 'when' clause should be straightforward and easy to understand. Avoid packing too much logic into a single 'when' statement.

Ranges are a powerful feature with 'when', but they should be used judiciously. Ensure that ranges are logical and do not overlap.

While 'when' is useful, overusing it can lead to cluttered code. If you find yourself with an excessively long list of 'when' clauses, consider refactoring your code.

If multiple 'when' clauses have the same outcome, combine them to streamline your code.

Always include an 'else' clause as a default case. This ensures that your code handles unexpected or unaccounted-for values.

By adhering to these best practices, you can use 'when' in Ruby effectively, making your code more readable, maintainable, and efficient. Remember, the goal is to write code that not only works but is also easy to understand and modify.

Overlapping Ranges

Forgetting the else clause, using 'when' for complex logic, misusing 'when' with non-comparable values, not using '==='.

When using 'when' in Ruby, certain common mistakes can lead to bugs or inefficient code. Being aware of these can help in writing cleaner, more effective code.

One common mistake is creating overlapping ranges in 'when' clauses. This can cause unexpected behavior as only the first matching condition will be executed.

Another mistake is omitting the 'else' clause . Without it, there's no catch-all for unanticipated values, which can lead to unpredictable results.

Using 'when' for complex logic can make your code hard to read and maintain. 'When' is best suited for simple, direct comparisons.

Be cautious when using 'when' with values that aren't directly comparable . This can lead to errors or unexpected behavior.

Understand that 'when' uses the '===' operator for comparison, which works differently than the '==' operator. This is particularly important when working with ranges or classes.

By avoiding these common pitfalls, you can ensure that your use of 'when' in Ruby is both effective and error-free. This leads to more robust and maintainable code.

Handling User Input

Categorizing data, simplifying complex conditions, integrating with other ruby features.

The 'when' clause in Ruby finds its utility in various real-world scenarios. These examples demonstrate how 'when' can be effectively used to simplify code and make it more readable.

Consider a program that responds to user input . Using 'when' makes it easy to handle different commands.

'When' is also useful for categorizing data , such as assigning a category based on age.

In scenarios with complex conditions , 'when' can greatly simplify the code, making it more readable.

'When' can be integrated with other Ruby features, like regular expressions , for more powerful pattern matching.

By incorporating 'when' into various scenarios like these, Ruby code becomes more efficient, organized, and easier to understand. These real-world examples highlight the practicality and adaptability of the 'when' clause in everyday programming tasks.

How does 'when' differ from an 'if' statement in Ruby?

'When' is specifically used within a case expression and is ideal for comparing a single variable against multiple values. An 'if' statement, on the other hand, is more flexible and can evaluate a variety of conditions, not limited to one variable.

Can 'when' clauses in Ruby handle multiple conditions for a single case?

Yes, a single 'when' clause can handle multiple conditions. You can list several values separated by commas, and if any of these values match the case expression, the code under that 'when' clause will execute.

Is it possible to use ranges with 'when' clauses in Ruby?

Absolutely, 'when' clauses can work with ranges. This is particularly useful for categorizing or grouping numbers, like defining age groups or scores.

How does Ruby compare the case statement's value with the 'when' conditions?

Ruby uses the '===' operator to compare the case statement's value with each 'when' condition. This operator allows for more flexibility than the standard '==' operator, as it can handle ranges, classes, and more.

Is it good practice to always include an 'else' clause in a case statement?

While not always necessary, it's generally good practice to include an 'else' clause to handle any unexpected values. This ensures that your code is robust and can gracefully handle unanticipated cases.

Let’s test your knowledge!

Understanding 'when' in Ruby Case Statements?

Subscribe to our newsletter, subscribe to be notified of new content on marketsplash..