ruby-core

Issue #9108 has been updated by Tom Wardrop.


Indeed, I'm still hanging out for this. Seems like such a common thing I run into, and I'm always surprised this functionality isn't built in. ```Hash#select { |k,v| {...}.include?(k) }``` is very verbose.

----------------------------------------
Feature #9108: Hash sub-selections
https://bugs.ruby-lang.org/issues/9108#change-60929

* Author: Tom Wardrop
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
----------------------------------------
Hi,

I seem to regularly have the requirement to work on a sub-set of key/value pairs within a hash. Ruby doesn't seem to provide a concise means of selecting a sub-set of keys from a hash. To give an example of what I mean, including how I currently achieve this:

```ruby
    sounds = {dog: 'woof', cat: 'meow', mouse: 'squeak', horse: 'nay', cow: 'moo'}
    domestic_sounds = sounds.select { |k,v| [:dog, :cat].include? k } #=> {dog: 'woof', cat: 'meow'}
```

I think a more concise and graceful solution to this would be to allow the Hash#[] method to take multiple arguments, returning a sub-hash, e.g.

```ruby
    domestic_sounds = sounds[:dog, :cat] #=> {dog: 'woof', cat: 'meow'}
```

I had a requirement in the current project I'm working on to concatenate two values in a hash. If this proposed feature existed, I could of just done this...

```ruby
    sounds[:dog, :cat].values.join #=> 'woofmeow'
```

You could do something similar for the setter also...

```ruby
    sounds[:monkey, :bat] = 'screech'
    sounds #=> {dog: 'woof', cat: 'meow', mouse: 'squeak', horse: 'nay', cow: 'moo', monkey: 'screech', bat: 'screech'}
```

Concise, convenient and readable. Thoughts?




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

Unsubscribe: <mailto:[email protected]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>