How to transform array with yielding a block?

Question

I trying to define a helper method that takes the Enumerable as arguments and should return processed values. Look at example of my problem.

>> def bar
>>   yield(->(x) { x.nil? })
>> end
>> bar { [nil, nil, 1].reject }
=> #<Enumerator: [nil, nil, 1]:reject>

I can't understand. An example below works as expected:

>> [nil, nil, 1].reject { |x| x.nil? }
=> [1]

What is missing here? Why i get a Enumerator instance instead of result?

Aleksei Matiushkin · Accepted Answer · 2015-04-30 10:00:09Z

2

The codeblock is not passed automagically to everything.

def bar 
   yield(->(x) { x.nil? })
end
bar do |p| 
  [nil, 1].reject &p
end

When you write

bar { ... }

you actually omit the yielded variable, exactly as in:

[1,nil].each { puts 'hey' }

answered Apr 30, 2015 at 10:00

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1 Comment

This is a very useful answer!