From: "zverok (Victor Shepelev) via ruby-core" <ruby-core@...>
Date: 2022-12-30T23:07:12+00:00
Subject: [ruby-core:111546] [Ruby master Bug#19278] Constructing subclasses of Data with positional arguments

Issue #19278 has been updated by zverok (Victor Shepelev).


> Your example didn't demonstrate this difference.

> I really don't understand point 3. 

> To be honest, I don't really care anymore.

It is a pity, after the thread this long. 

If you would've cared, you'd maybe spent a few minutes drafting an `initialize` that would work the way you want **and maintained the contract**, and my points would probably become more obvious.

(FTR, the starting example of the ticket wasn't really illustrative because the point of creating `Data` with no members and then adding instance variables in `initialize` is unclear. `Data` is a value object that is good for value object goals, not a generic "just base class for anything".)

But it is what it is, I think.

----------------------------------------
Bug #19278: Constructing subclasses of Data with positional arguments
https://bugs.ruby-lang.org/issues/19278#change-100910

* Author: tenderlovemaking (Aaron Patterson)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) [arm64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
I'd expect both of the following subclasses to work, but the subclass that uses positional parameters raises an exception:

```ruby
Foo = Data.define

class Bar < Foo
  def initialize foo:
    p foo
  end
end

class Baz < Foo
  def initialize foo
    p foo
  end
end

Bar.new foo: 1 # Prints 1
Baz.new 1    # Raises ArgumentError
```

I'd expect the subclass that uses positional arguments to work.



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