From: "zverok (Victor Shepelev) via ruby-core" <ruby-core@...>
Date: 2023-03-29T06:34:52+00:00
Subject: [ruby-core:113037] [Ruby master Feature#19555] Allow passing default options to `Data.define`

Issue #19555 has been updated by zverok (Victor Shepelev).





This is not simple as it seems (that's why we abstained of introducing something like that).



Imagine this:



```ruby

Point = Data.define(:x, :y, tags: [])



p1 = Point.new(1, 2)

p1.tags << 'foo'



p2 = Point2.new(3, 4)

p2.tags #=>?

```



In naive implementation, `p1.tags` is the same ary as passed for default, and `p1.tags << 'foo'` adjusts the default value.



In less naive implementation, we need probably `.dup` defaults, which still might be not enough or impossible.



Yes, mutable values are kinda against Data idea, but it doesn���t mean nobody will do that. 



----------------------------------------

Feature #19555: Allow passing default options to `Data.define`

https://bugs.ruby-lang.org/issues/19555#change-102574



* Author: p8 (Petrik de Heus)

* Status: Open

* Priority: Normal

----------------------------------------

Defining a subclass of `Data` with default attributes can currently be done by overriding `intialize`:

```ruby

class Point < Data.define(:x, :y, :z)

  def initialize(x:, y:, z: 0) = super

end



p Point.new(1, 2)

#=> #<data Point x=1, y=2, z=0>

```



It would be nice if we could do it in `define` as well:



```ruby

Point = Data.define(:x, :y, z: 0)

```







-- 

https://bugs.ruby-lang.org/

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