[ruby-core:77522] [Ruby trunk Feature#12820] Shorter syntax for assigning a method argument to an instance variable

Issue #12820 has been updated by Matthew Kerwin.


See:
* #12578 Instance Variables Assigned In parameters ( ala Crystal? )
* #5825 Sweet instance var assignment in the object initializer
* #8563 Instance variable arguments
* #12023 Allow ivars to be used as method arguments

Is this now the most-duplicated feature request in Ruby?

----------------------------------------
Feature #12820: Shorter syntax for assigning a method argument to an instance variable
https://bugs.ruby-lang.org/issues/12820#change-60786

* Author: Fabio Pugliese Ornellas
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
Hello,

The pattern:

~~~
class Person
  def initialize(name:)
    @name = name
    @age  = 0
  end
end
~~~

is so common, that Cristal Programming Language has a shortcut for it:
https://crystal-lang.org/docs/syntax_and_semantics/methods_and_instance_variables.html

~~~
class Person
  def initialize(@name : String)
    @age = 0
  end
end
~~~

This is a feature request to implement the same style to Ruby syntax, supporting both isolated parameters and Hash style parameters. Eg:

~~~
class Person
  attr_reader :name, :age
  def initialize(@name, @age:)
  end
end
fabio = Person.new("Fabio", age: 34)
fabio.name #=> "Fabio"
fabio.age  #=> 34
~~~

This will be very useful in methods that accept a lot of parameters and certainly will avoid bugs due to decreased duplicated code (eg: addind a new parameter to a method, and forgetting to set the instance variable to it). Other than implementing support for the syntax itself, I believe RDoc would also have to be updated, not to expose the "@" on documentation (as it is not relevant there).

What do you think?

Thank you.



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