Ruby lambda syntax issue

Question

I have some Ruby code

def a(x, y)
  puts x, y.call
end

a :a, -> do
  [1, 2, 3].map! do |j|
    j
  end
end

I'm almost sure that it's correct, editor highlights it as correct, but I have such exception:

SyntaxError: (irb):6: syntax error, unexpected keyword_do_block, expecting keyword_end
  [1, 2, 3].map! do |j|
                   ^
(irb):9: syntax error, unexpected keyword_end, expecting end-of-input

It may be related to usage of do and end instead of {}, since the block applies to the last expression here, not to the a method call. And it works with {} instead of do and end. But it also works with do/end and without inner block. So it may be a false trail. — Marek Lipka
– Marek Lipka, Commented Sep 10, 2015 at 11:17
Yes, It works, but I thought that {..} and do..end are equivalent — Alex Tonkonozhenko
– Alex Tonkonozhenko, Commented Sep 10, 2015 at 11:19

Roope Hakulinen · Accepted Answer · 2015-09-10 11:21:49Z

4

If I'm not totally mistaken, you need to wrap the method call in parentheses like this

def a(x, y)
  puts x, y.call
end

a(:a, -> do
  [1, 2, 3].map! do |j|
    j
  end
end)

Now there still is problem that you are passing two parameters to puts where only one is allowed, so you would need to concatenate the string with + or some other way.

answered Sep 10, 2015 at 11:21

Roope Hakulinen

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