[ruby-core:91032] [Ruby trunk Feature#15526] New way to destruct an object hash

[zverok.offline@gmail.com]

Issue #15526 has been updated by zverok (Victor Shepelev).


> Admit it, you only wanted to use `.then`

That's absolutely not the point. The real point here is: 

1) Ruby has very consistent "argument **deconstruction**" rules. Basically, "it is deconstructed the same way it is constructed", e.g., if you can _call_ (construct) with arguments like `meth(a, *b, c: 1, d: 2, **e)`, you can also _receive_ (deconstruct) arguments exactly the same way: `a, *b, c:, d: nil, **e`.

2) The deconstruction is fully enabled in arguments (including keyword arguments) to procs and methods

3) Initially (before keyword arguments), the variable assignment had the same "expressive power", e.g. you could define a method like 

```ruby
def meth(a, b, *rest)
```
...and you could assign variables the same way:

```ruby
a, b, *rest = [1, 2, 3, 4]
```

4) When keyword arguments were introduced, there was no matching syntax for variable assignment. If it **would** exist, it most probably **should** look this way (same as arguments, remember):

```ruby
a:, b:, **kwrest = {a: 1, b: 2, c: 3, d: 4}
```
It obviously looks confusing (and would probably be hard for the parser), and I believe that's the reason it was NOT added to the language.

5) I don't think adding "orphan feature" (looking like nothing else in the language) just for the sake of this particular case would be ever accepted; and I don't think it should.

6) In the meantime, "chainable" code style (with `Enumerable` and `#then`) allows to embrace argument deconstruction in its full force:
```ruby
config.then { |host:, port: 8080, **rest|
```
...which is NOT the main (and obviously not the only) reason to use this style, just a nice side-effect of its consistency with the rest of the language.

----------------------------------------
Feature #15526: New way to destruct an object hash
https://bugs.ruby-lang.org/issues/15526#change-76253

* Author: alissonbruno.sa (Alisson  Santos)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
JavaScript has a nice a neat way to destruct objects.

~~~ javascript
const person = { name: "John Doe", age: 33 };
const { name, age } =  person;
~~~

Erlang has a similar way to destruct a tuple:
~~~ erlang
Person = {"John Doe", 33}
{Name, Age} = Person
~~~

I think it's very handy and would be nice if we have something similar in Ruby.

~~~ ruby
config = { host: 'localhost', port: 3000 } 
{ host, port } = config
~~~

I know Ruby has Hash#values_at, but I think this way it's more readable and understandable

What do you guys think?




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