method assignment operator ruby

If and Unless Expressions

If and unless modifiers, case expressions.

Break, Redo, and Next

Variable Scope and Loops

Ruby Programming/Syntax/Operators

• 1.1 Complete List and Precedence
• 1.2 Other operators
• 1.3 Assignment
• 2.1 Local Scope
• 2.2 Global scope
• 2.3 Instance scope
• 2.4 Class scope
• 3 Default scope
• 4 Local scope gotchas
• 5 Logical And
• 6 Logical Or
• 7 References

Complete List and Precedence

Higher precedence (lower number in the above table) operators have their immediate arguments evaluated first. Precedence order can be altered with () blocks. For example, because * has higher precedence than +, then: 1 + 2 * 3 == 7 (1 + 2) * 3 == 9

Association direction controls which operators have their arguments evaluated first when multiple operators with the same precedence appear in a row. For example, because - has left association:

1 – 2 – 3 == (1 – 2) – 3 == -1 – 3 == -4

instead of:

1 – 2 – 3 == 1 – (2 – 3) == 1 - -1 == 0

Because ** has right association:

2 ** 3 ** 2 == 2 ** (3 ** 2) == 2 ** 9 == 512

2 ** 3 ** 2 == (2 ** 3) ** 2 == 8 ** 2 == 64

{} blocks have lower precedence than the above operators, followed by do/end blocks. Array accesses with [] can be thought of as having a higher precedence than any above operator.

The operators ** through !~ can be overridden (defined for new classes, or redefined for existing operations).

Note that rescue, if, unless, while, and until are operators when used as modifiers in one-liners (as in the above examples) but can also be used as keywords.

Other operators

The dot operator . is used for calling methods on objects, also known as passing a message to the object.

Ruby 2.3.0 introduced the safe navigation operator &. , also known as the "lonely operator". [2] This allows replacing

An equivalent .dig() method was introduced for hashes and arrays:

are safer versions of:

The safe navigation operator will raise an error if a requested method, key, or index is not available; unlike the technique of using try() for this purpose, which will return nil. [3]

Yukihiro Matsumoto considered ! ?. and .? before settling on &. because: [4]

• ?. conflicts with *?
• ?. is used by other languages, thus .? is confusingly similar but different
• ! conflicts with "not" logic
• ? is already used by convention for functions that return booleans
• &. is reminiscent of the && syntax the operator is replacing

!! is sometimes seen, but this is simply the ! operator twice. It is used to force the following expression to evaluate to a boolean. This technique is considered non-idiomatic and poor programming practice, because there are more explicit ways to force such a conversion (which is rarely needed to begin with).

Assignment in Ruby is done using the equal operator "=". This is both for variables and objects, but since strings, floats, and integers are actually objects in Ruby, you're always assigning objects.

Self assignment

A frequent question from C and C++ types is "How do you increment a variable? Where are ++ and -- operators?" In Ruby, one should use x+=1 and x-=1 to increment or decrement a variable.

Multiple assignments

Conditional assignment

Operator ||= is a shorthand form that closely resembles the expression: [5]

Operator ||= can be shorthand for code like:

In same way &&= operator works:

Operator &&= is a shorthand form of the expression:

In Ruby there's a local scope, a global scope, an instance scope, and a class scope.

Local Scope

This error appears because this x(toplevel) is not the x(local) inside the do..end block the x(local) is a local variable to the block, whereas when trying the puts x(toplevel) we're calling a x variable that is in the top level scope, and since there's not one, Ruby protests.

Global scope

This output is given because prefixing a variable with a dollar sign makes the variable a global.

Instance scope

Within methods of a class, you can share variables by prefixing them with an @.

Class scope

A class variable is one that is like a "static" variable in Java. It is shared by all instances of a class.

Here's a demo showing the various types:

This will print the two lines "kiwi" and "kiwi told you so!!", then fail with a undefined local variable or method 'localvar' for #<Test:0x2b36208 @instvar="kiwi"> (NameError). Why? Well, in the scope of the method print_localvar there doesn't exists localvar, it exists in method initialize(until GC kicks it out). On the other hand, class variables '@@classvar' and '@instvar' are in scope across the entire class and, in the case of @@class variables, across the children classes.

Class variables have the scope of parent class AND children, these variables can live across classes, and can be affected by the children actions ;-)

This new child of Test also has @@classvar with the original value newvar.print_classvar. The value of @@classvar has been changed to 'kiwi kiwi waaai!!' This shows that @@classvar is "shared" across parent and child classes.

Default scope

When you don't enclose your code in any scope specifier, ex:

it affects the default scope, which is an object called "main".

For example, if you had one script that says

and other_script.rb says

They could share variables.

Note however, that the two scripts don't share local variables.

Local scope gotchas

Typically when you are within a class, you can do as you'd like for definitions, like.

And also, procs "bind" to their surrounding scope, like

However, the "class" and "def" keywords cause an *entirely new* scope.

You can get around this limitation by using define_method, which takes a block and thus keeps the outer scope (note that you can use any block you want, to, too, but here's an example).

Here's using an arbitrary block

Logical And

The binary "and" operator will return the logical conjunction of its two operands. It is the same as "&&" but with a lower precedence. Example:

The binary "or" operator will return the logical disjunction of its two operands. It is the same as "||" but with a lower precedence. Example:

• ↑ http://ruby-doc.org/core-2.4.0/doc/syntax/precedence_rdoc.html
• ↑ https://www.ruby-lang.org/en/news/2015/12/25/ruby-2-3-0-released/
• ↑ http://blog.rubyeffect.com/ruby-2-3s-lonely-operator/
• ↑ https://bugs.ruby-lang.org/issues/11537
• ↑ http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.html

• Book:Ruby Programming

Navigation menu

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:

• Ruby Basics
• Ruby - Home
• Ruby - Overview
• Ruby - Environment Setup
• Ruby - Syntax
• Ruby - Classes and Objects
• Ruby - Variables

Ruby - Operators

• Ruby - Comments
• Ruby - IF...ELSE
• Ruby - Loops
• Ruby - Methods
• Ruby - Blocks
• Ruby - Modules
• Ruby - Strings
• Ruby - Arrays
• Ruby - Hashes
• Ruby - Date & Time
• Ruby - Ranges
• Ruby - Iterators
• Ruby - File I/O
• Ruby - Exceptions
• Ruby Advanced
• Ruby - Object Oriented
• Ruby - Regular Expressions
• Ruby - Database Access
• Ruby - Web Applications
• Ruby - Sending Email
• Ruby - Socket Programming
• Ruby - Ruby/XML, XSLT
• Ruby - Web Services
• Ruby - Tk Guide
• Ruby - Ruby/LDAP Tutorial
• Ruby - Multithreading
• Ruby - Built-in Functions
• Ruby - Predefined Variables
• Ruby - Predefined Constants
• Ruby - Associated Tools
• Ruby Useful Resources
• Ruby - Quick Guide
• Ruby - Useful Resources
• Ruby - Discussion
• Ruby - Ruby on Rails Tutorial
• Selected Reading
• UPSC IAS Exams Notes
• Developer's Best Practices
• Questions and Answers
• Effective Resume Writing
• HR Interview Questions
• Computer Glossary

Ruby supports a rich set of operators, as you'd expect from a modern language. Most operators are actually method calls. For example, a + b is interpreted as a.+(b), where the + method in the object referred to by variable a is called with b as its argument.

For each operator (+ - * / % ** & | ^ << >> && ||), there is a corresponding form of abbreviated assignment operator (+= -= etc.).

Ruby Arithmetic Operators

Assume variable a holds 10 and variable b holds 20, then −

Ruby Comparison Operators

Ruby Assignment Operators

Ruby Parallel Assignment

Ruby also supports the parallel assignment of variables. This enables multiple variables to be initialized with a single line of Ruby code. For example −

This may be more quickly declared using parallel assignment −

Parallel assignment is also useful for swapping the values held in two variables −

Ruby Bitwise Operators

Bitwise operator works on bits and performs bit by bit operation.

Assume if a = 60; and b = 13; now in binary format they will be as follows −

The following Bitwise operators are supported by Ruby language.

Ruby Logical Operators

The following logical operators are supported by Ruby language

Ruby Ternary Operator

There is one more operator called Ternary Operator. It first evaluates an expression for a true or false value and then executes one of the two given statements depending upon the result of the evaluation. The conditional operator has this syntax −

Ruby Range Operators

Sequence ranges in Ruby are used to create a range of successive values - consisting of a start value, an end value, and a range of values in between.

In Ruby, these sequences are created using the ".." and "..." range operators. The two-dot form creates an inclusive range, while the three-dot form creates a range that excludes the specified high value.

Ruby defined? Operators

defined? is a special operator that takes the form of a method call to determine whether or not the passed expression is defined. It returns a description string of the expression, or nil if the expression isn't defined.

There are various usage of defined? Operator

For Example

Ruby Dot "." and Double Colon "::" Operators

You call a module method by preceding its name with the module's name and a period, and you reference a constant using the module name and two colons.

The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module.

Remember in Ruby, classes and methods may be considered constants too.

You need to just prefix the :: Const_name with an expression that returns the appropriate class or module object.

If no prefix expression is used, the main Object class is used by default.

Here are two examples −

Second Example

Ruby Operators Precedence

The following table lists all operators from highest precedence to lowest.

NOTE − Operators with a Yes in the method column are actually methods, and as such may be overridden.

• Ruby Tutorial
• Ruby Operators Precedence
• Ruby Arithmetic Operators
• Ruby Comparison Operators

Ruby Assignment Operators

• Ruby Parallel Assignment
• Ruby Bitwise Operators
• Ruby Logical Operators
• Ruby Ternary operator
• Ruby Defined Operators
• Ruby Dot And Double Colon Operators

Assignment Operators

In Ruby assignment operator is done using the equal operator "=". This is applicable both for variables and objects, as strings, floats, and integers are actually objects in Ruby, you're always assigning objects.

Example: Ruby assignment operator

Previous: Ruby Comparison Operators Next: Ruby Parallel Assignment

Follow us on Facebook and Twitter for latest update.

• Weekly Trends and Language Statistics

Ruby Language

• Getting started with Ruby Language
• Awesome Book
• Awesome Community
• Awesome Course
• Awesome Tutorial
• Awesome YouTube
• Blocks and Procs and Lambdas
• C Extensions
• Casting (type conversion)
• Catching Exceptions with Begin / Rescue
• Command Line Apps
• Control Flow
• Design Patterns and Idioms in Ruby
• Destructuring
• Dynamic Evaluation
• Enumerable in Ruby
• Enumerators
• Environment Variables
• File and I/O Operations
• Gem Creation/Management
• Generate a random number
• Getting started with Hanami
• Implicit Receivers and Understanding Self
• Inheritance
• Installation
• instance_eval
• Introspection
• Introspection in Ruby
• JSON with Ruby
• Keyword Arguments
• Loading Source Files
• Message Passing
• Metaprogramming
• method_missing
• Monkey Patching in Ruby
• Multidimensional Arrays
• Operating System or Shell commands
• Assignment Operators
• Comparison Operators
• OptionParser
• Pure RSpec JSON API testing
• Recursion in Ruby
• Refinements
• Regular Expressions and Regex Based Operations
• Ruby Access Modifiers
• Ruby Version Manager
• Singleton Class
• Special Constants in Ruby
• Splat operator (*)
• Variable Scope and Visibility

Ruby Language Operators Assignment Operators

Fastest entity framework extensions, simple assignment.

= is a simple assignment. It creates a new local variable if the variable was not previously referenced.

This will output:

Parallel Assignment

Variables can also be assigned in parallel, e.g. x, y = 3, 9 . This is especially useful for swapping values:

Abbreviated Assignment

It's possible to mix operators and assignment. For example:

Shows the following output:

Various operations can be used in abbreviated assignment:

Got any Ruby Language Question?

• Advertise with us
• Cookie Policy
• Privacy Policy

Get monthly updates about new articles, cheatsheets, and tricks.

Ruby Tricks, Idiomatic Ruby, Refactorings and Best Practices

Conditional assignment.

Ruby is heavily influenced by lisp. One piece of obvious inspiration in its design is that conditional operators return values. This makes assignment based on conditions quite clean and simple to read.

There are quite a number of conditional operators you can use. Optimize for readability, maintainability, and concision.

If you're just assigning based on a boolean, the ternary operator works best (this is not specific to ruby/lisp but still good and in the spirit of the following examples!).

If you need to perform more complex logic based on a conditional or allow for > 2 outcomes, if / elsif / else statements work well.

If you're assigning based on the value of a single variable, use case / when A good barometer is to think if you could represent the assignment in a hash. For example, in the following example you could look up the value of opinion in a hash that looks like {"ANGRY" => comfort, "MEH" => ignore ...}

• Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers
• Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand
• OverflowAI GenAI features for Teams
• OverflowAPI Train & fine-tune LLMs
• Labs The future of collective knowledge sharing
• About the company Visit the blog

Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Get early access and see previews of new features.

How do I use the conditional operator (? :) in Ruby?

How is the conditional operator ( ? : ) used in Ruby?

For example, is this correct?

• ternary-operator
• conditional-operator

• 1 yes, I think, but I also think you could accomplish that by: question=question[0,20] If it was smaller than 20, it won't change it any. –  DGM Commented Nov 23, 2010 at 5:06
• i also need to add a '...' if length is greater than 20 –  Mithun Sreedharan Commented Nov 23, 2010 at 5:32
• 1 Be careful blindly chopping off a line at a given column. You can end up cutting a word midway then appending the elipsis ('...'), which looks bad. Instead, look for a nearby punctuation or whitespace character, and truncate there. Only if there is no better breaking point nearby should you truncate mid-word. –  the Tin Man Commented Nov 23, 2010 at 6:11

7 Answers 7

It is the ternary operator , and it works like in C (the parenthesis are not required). It's an expression that works like:

However, in Ruby, if is also an expression so: if a then b else c end === a ? b : c , except for precedence issues. Both are expressions.

Note that in the first case parenthesis are required (otherwise Ruby is confused because it thinks it is puts if 1 with some extra junk after it), but they are not required in the last case as said issue does not arise.

You can use the "long-if" form for readability on multiple lines:

• Puts 0 ? 2 : 3 also gives 2 as a result. Why is that? –  X_Trust Commented Jul 9, 2014 at 15:23
• 19 @X_Trust In Ruby, the only falsy values are nil and false . Not very usual, indeed. –  Kroltan Commented Jul 25, 2014 at 14:04
• This is a good explanation, but like almost every explanation I've seen, the behavior is essentially described as condition ? value if true : value if false . I think a much better way to describe the behavior is this: condition ? value if TRUTHY : value if FALSEY . The difference is subtle but very important to understand. –  user16452228 Commented Feb 10, 2022 at 19:12

• Terse but explains what it does. –  the Tin Man Commented Oct 2, 2014 at 23:17
• 4 Small edit puts (true ? "true" : "false") with parenthesis. Otherwise the order of operations is not clear. When I first read this I was confused as I read it as (puts true) ? "true" : "false" then expected puts to return the boolean which then became the string value. –  Fresheyeball Commented Aug 25, 2015 at 23:16

Your use of ERB suggests that you are in Rails. If so, then consider truncate , a built-in helper which will do the job for you:

• This is great! what I exactly want to do!! –  Mithun Sreedharan Commented Nov 24, 2010 at 4:07
• 12 This is years late, but I was very impressed with this answer as it jumped past all the syntactical aspects and went right to what the questioner was trying to accomplish. –  Mike Buckbee Commented May 5, 2014 at 5:21
• 2 +1, but erb does not necessarily imply rails (Sinatra, standalone ERB, etc). –  tew Commented Aug 2, 2014 at 8:43

@pst gave a great answer, but I'd like to mention that in Ruby the ternary operator is written on one line to be syntactically correct, unlike Perl and C where we can write it on multiple lines:

Normally Ruby will raise an error if you attempt to split it across multiple lines, but you can use the \ line-continuation symbol at the end of a line and Ruby will be happy:

This is a simple example, but it can be very useful when dealing with longer lines as it keeps the code nicely laid out.

It's also possible to use the ternary without the line-continuation characters by putting the operators last on the line, but I don't like or recommend it:

I think that leads to really hard to read code as the conditional test and/or results get longer.

I've read comments saying not to use the ternary operator because it's confusing, but that is a bad reason to not use something. By the same logic we shouldn't use regular expressions, range operators (' .. ' and the seemingly unknown "flip-flop" variation). They're powerful when used correctly, so we should learn to use them correctly.

Why have you put brackets around true ?

Consider the OP's example:

Wrapping the conditional test helps make it more readable because it visually separates the test:

Of course, the whole example could be made a lot more readable by using some judicious additions of whitespace. This is untested but you'll get the idea:

Or, more written more idiomatically:

It'd be easy to argument that readability suffers badly from question.question too.

• 2 If multi-line, why not just use if...else...end? –  Wayne Conrad Commented Nov 23, 2010 at 16:44
• 2 Because of too many years working in Perl and C? I use either, depending on the situation and whether one is visually clearer than the other. Sometimes if/else is too verbose, sometimes ?: is ugly. –  the Tin Man Commented Nov 23, 2010 at 16:47
• 1 @WayneConrad The if has at least one problem explained in this answer: stackoverflow.com/a/4252945/2597260 Compare a few ways of using multiline if/ternary operator: gist.github.com/nedzadarek/0f9f99755d42bad10c30 –  Darek Nędza Commented Dec 17, 2014 at 18:14
• Why have you put brackets around true ? –  Zac Commented Oct 7, 2016 at 17:05
• 2 Because true is actually sitting in for what would be an expression that evaluates to true or false . It's better to visually delimit those since ternary statements can quickly devolve into visual noise, reducing readability which affects maintainability. –  the Tin Man Commented Oct 7, 2016 at 17:17

A simple example where the operator checks if player's id is 1 and sets enemy id depending on the result

And I found a post about to the topic which seems pretty helpful.

• 4 Why not enemy_id = player_id == 1 ? 2 : 1 ? –  Aaron Blenkush Commented Mar 19, 2018 at 19:51
• 1 @AaronBlenkush Thanks for the elegant input. I am still in noob level, probably it is why :) –  devwanderer Commented Mar 21, 2018 at 7:01

Easiest way:

since param_a is not equal to param_b then the result 's value will be Not same!

The code condition ? statement_A : statement_B is equivalent to

Your Answer

Reminder: Answers generated by artificial intelligence tools are not allowed on Stack Overflow. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged ruby ternary-operator conditional-operator or ask your own question .

• The Overflow Blog
• Scaling systems to manage all the metadata ABOUT the data
• Navigating cities of code with Norris Numbers
• Featured on Meta
• We've made changes to our Terms of Service & Privacy Policy - July 2024
• Bringing clarity to status tag usage on meta sites
• Feedback requested: How do you use tag hover descriptions for curating and do...

Hot Network Questions

• A study on the speed of gravity
• How do you "stealth" a relativistic superweapon?
• What is the purpose of toroidal magnetic field in tokamak fusion device?
• Why is this white line between the two vertical boxes?
• Are there jurisdictions where an uninvolved party can appeal a court decision?
• Many and Many of - a subtle difference in meaning?
• What connotation does "break out the checkbook" have?
• I submitted a paper and later realised one reference was missing, although I had written the authors in the body text. What could happen?
• What exactly is component based architecture and how do I get it to work?
• Would donations count as revenue from a free software?
• How would a culture living in an extremely vertical environment deal with dead bodies?
• How to cite a book if only its chapters have DOIs?
• Who became an oligarch after the collapse of the USSR
• Venus’ LIP period starts today, can we save the Venusians?
• Do "Whenever X becomes the target of a spell" abilities get triggered by counterspell?
• can a CPU once removed retain information that poses a security concern?
• Trying to understand an attack showcased in a viral YouTube video
• How did Jason Bourne know the garbage man isn't CIA?
• Power line crossing data lines via the ground plane
• Age is just a number!
• Terminal autocomplete (tab) not completing when changing directory up one level (cd ../)
• Sulphur smell in Hot water only
• Questions about best way to raise the handlebar on my bike
• Why was I was allowed to bring 1.5 liters of liquid through security at Frankfurt Airport?