Feature #20914: Constructor Parameter Shortcuts

• Status: Closed
• Assignee: -
• Target version: -

[artemb (Artem Borodkin)]

Constructor Parameter Shortcuts

I propose adding a new syntax to simplify the constructor definition in the classes. Defining a constructor often involves repetitive assignments of parameters to instance variables. This pattern is verbose and can easily become cumbersome, especially in classes with many instance variables. The proposed syntax allows instance variables to be automatically assigned from constructor arguments, improving code clarity and brevity.

Basic Usage:

• Current:

  class User
    def initialize(name, age, email = nil)
      @name = name
      @age = age
      @email = email
    end
  end
  

• Proposed:

  class User
    def initialize(@name, @age, @email = nil) =
  end
  

Named Parameters:

• Current:

  class Product
    def initialize(name:, price:, description: 'No description available')
      @name = name
      @price = price
      @description = description
    end
  end
  
  product = Product.new(name: 'Laptop', price: 1000)
  

• Proposed:

  class Product
    def initialize(@name:, @price:, @description: 'No description available') =
  end
  
  product = Product.new(name: 'Laptop', price: 1000)
  

Mixing Named and Positional Parameters:

• Current:

  class Booking
    def initialize(date, time, customer:, notes: '')
      @date = date
      @time = time
      @customer = customer
      @notes = notes
    end
  end
  
  booking = Booking.new('2023-04-01', '14:00', customer: 'Alice', notes: 'First-time client')
  

• Proposed:

  class Booking
    def initialize(@date, @time, @customer:, @notes: '') =
  end
  
  booking = Booking.new('2023-04-01', '14:00', customer: 'Alice', notes: 'First-time client')
  

[mame (Yusuke Endoh)]

• Related to Feature #5825: Sweet instance var assignment in the object initializer added

[nobu (Nobuyoshi Nakada)]

  def initialize(@name, @age, @email = nil) =

What is the equal sign at the end?
nil is missed?

[artemb (Artem Borodkin)]

You’re absolutely right; this part does seem ambiguous. I initially added it as an empty block, modeled after the short syntax, like this:

def initialize(name, age, email = nil) = (@name, @age, @email = name, age, email)

What do you think about this option:

def initialize(@name, @age, @email = nil) = ()

The nil is also possible

def initialize(@name, @age, @email = nil) = nil

[mame (Yusuke Endoh)]

What do you think about this option:

Then this proposal is almost the same as #5825.

[artemb (Artem Borodkin)]

Thank you! This appears to be literally the same proposal, so it can be closed.
I will review #5825 and follow for updates.

[mame (Yusuke Endoh)]

• Status changed from Open to Closed