From: "ozydingo (Andrew Schwartz) via ruby-core" <ruby-core@...>
Date: 2025-02-01T06:37:47+00:00
Subject: [ruby-core:120852] [Ruby master Feature#19555] Allow passing default options to `Data.define`

Issue #19555 has been updated by ozydingo (Andrew Schwartz).


I've found the need for something like this as well, I have a use case where it's getting repetitive and distractingly verbose to build out the `Data` blocks just for a number of defaults. The mutable defaults is a really good point, though it's not too dissimilar from existing behavior in Ruby's Hash with defaults --

```rb
h = Hash.new([])
h[1] << 'foo'

h[2] #=> ['foo']
```

So in a sense there is prior art here and a pattern that Rubyists already have to be aware of.

----------------------------------------
Feature #19555: Allow passing default options to `Data.define`
https://bugs.ruby-lang.org/issues/19555#change-111728

* Author: p8 (Petrik de Heus)
* Status: Open
----------------------------------------
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)
```



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