From: 6ftdan@...
Date: 2015-11-18T19:13:21+00:00
Subject: [ruby-core:71563] [Ruby trunk - Feature #11690] Update Hash during	multiple assignment

Issue #11690 has been updated by Daniel P. Clark.


If we wanted to avoid chomping the equals sign on methods that have the equals already we'd have to write in a check for that.  But I'm not sure that would be as performant.

~~~ruby
class Applicable
  def initialize(obj)
    @target = obj
  end
  def method_missing(m, *args)
    m = @target.respond_to?(m) ? m : m.to_s.chomp('=')
    @target.__send__(m, *args)
  end
  def respond_to_missing?(m)
    @target.respond_to?(m.to_s.chomp('='))
  end
end

x = {a: 1, b: 2}

x.apply.update, y ,z = {c: 3}, 6, 7

# Hash still responds to :[]= method now after :apply
x.apply[:z] = 0

x
# => {:a=>1, :b=>2, :c=>3, :z=>0}

~~~

----------------------------------------
Feature #11690: Update Hash during multiple assignment
https://bugs.ruby-lang.org/issues/11690#change-54945

* Author: Daniel P. Clark
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
Given that we can assign multiple variables at once

~~~ruby
a,b,c = 1,2,3
~~~

It would be nice to be able to update a Hash during multiple assignment rather than replacing it.  Currently

~~~ruby
x = {a: 1, b: 2}
x, y ,z = {c: 3}, 6, 7
x
# => {c: 3}
~~~

What I propose is adding `Hash#update=` to permit updating during multiple assignment.

~~~ruby
class Hash
  def update=(h)
    update(h)
  end
end

x = {a: 1, b: 2}

x.update, y ,z = {c: 3}, 6, 7
x
# => {a: 1, b: 2, c: 3}
~~~

This would be most useful in scenarios where a method or proc return multiple values.  When the method returns the values we don't normally know the key outside where the hash assignment is.

~~~ruby
example = proc { [{:hi => :hello}, 5] }

hash = {}

# Currently in Ruby with an Unknown key multiple assignment isn't an option
hash[????], current = example.call

# We currently have to two step it
result, current = example.call
hash.update(result)
~~~

But with `Hash#update=` we don't have to know the key.



-- 
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