ruby-core

Issue #8895 has been updated by Yukihiro Matsumoto.


The proposed syntax is much harder to implement than it looks. It conflicts with Hash literals. As a result, humans can be confused as well.

Probably this kind of problems should be addressed by pattern matching, which we are considering to add to Ruby in the future.

Matz.



----------------------------------------
Feature #8895: Destructuring Assignment for Hash
https://bugs.ruby-lang.org/issues/8895#change-58683

* Author: Jack Chen
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------

Given Ruby already supports destructuring assignment with Array (a, b = [1, 2]), I propose destructuring assignments for Hash.

Basic example
-------------

```ruby
  params = {name: "John Smith", age: 42}
  {name: name, age: age} = params

  # name == "John Smith"
  # age == 42
```

This would replace a common pattern of assigning hash values to local variables to work with.

General syntax
--------------

```ruby
  { <key-expr> => <variable_name>, … } = <object that responds to #[]>

  # Symbols
  { foo: bar } = { foo: "bar" }
  bar == "bar"

  # Potential shorthand
  { foo } = { foo: "bar" }
  foo == "bar"
```

Use cases
---------

```ruby
  # MatchData
  { username: username, age: age } = "user:jsmith age:42".match(/user:(?<username>\w+) age:(?<age>\d+)/)
  username == "jsmith"
  age == "42"
```

Edge cases
----------

```ruby
  # Variable being assigned to more than once should use the last one
  { foo: var, bar: var } = {foo: 1, bar: 2}
  var == 2
```

Thoughts?





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