[ruby-core:120032] [Ruby master Feature#20914] Constructor Parameter Shortcuts

28 Nov 2024

      Issue #20914 has been updated by nobu (Nobuyoshi Nakada).

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

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

----------------------------------------
Feature #20914: Constructor Parameter Shortcuts
https://bugs.ruby-lang.org/issues/20914#change-110773

* Author: artemb (Artem Borodkin)
* Status: Open
----------------------------------------
# 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**:
     ```ruby
     class User
       def initialize(name, age, email = nil)
         @name = name
         @age = age
         @email = email
       end
     end
     ```

   - **Proposed**:
     ```ruby
     class User
       def initialize(@name, @age, @email = nil) =
     end
     ```

**Named Parameters**:

   - **Current**:
     ```ruby
     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**:
     ```ruby
     class Product
       def initialize(@name:, @price:, @description: 'No description available') =
     end

     product = Product.new(name: 'Laptop', price: 1000)
     ```

**Mixing Named and Positional Parameters**:

   - **Current**:
     ```ruby
     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**:
     ```ruby
     class Booking
       def initialize(@date, @time, @customer:, @notes: '') =
     end

     booking = Booking.new('2023-04-01', '14:00', customer: 'Alice', notes: 'First-time client')
     ```

-- 
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