Here's a neat Ruby trick for fans of Symbol#to_proc.
This magical method, introduced by both Rails and Ruby 1.9, lets you do things like this:
> %w(1 2 3 4 5).map &:to_i
=> [1, 2, 3, 4, 5]
=> [1, 2, 3, 4, 5]
And that proc can, of course, take multiple parameters:
[1,2,3,4].zip([2,3,4,5])
=> [[1, 2], [2, 3], [3, 4], [4, 5]]> [1,2,3,4].zip([2,3,4,5]).map &:sum
=> [3, 5, 7, 9]
=> [[1, 2], [2, 3], [3, 4], [4, 5]]> [1,2,3,4].zip([2,3,4,5]).map &:sum
=> [3, 5, 7, 9]
However, if you want to "close" a value into the proc, you're out of luck, so you have to define a block old-school-style:
> %w(kung ruby bar).map { |e| e + "-fu" }
=> ["kung-fu", "ruby-fu", "bar-fu"]
=> ["kung-fu", "ruby-fu", "bar-fu"]
But check out the following little hack:
class Array
def to_proc
lambda { |target| target.send(*self) }
end
end
def to_proc
lambda { |target| target.send(*self) }
end
end
Now look what you can do:
> %w(kung ruby bar).map &[:+, "-fu"]
=> ["kung-fu", "ruby-fu", "bar-fu"]
=> ["kung-fu", "ruby-fu", "bar-fu"]
What do you think? Handy? Disgusting? Leave a comment to let me know!
Update: apparently others have had similar ideas, but with different semantics. So perhaps this trick is a little too opaque...
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Hi Steve.
Array#to_procis a clever trick. Too clever in my opinion. As much as I likeSymbol#to_proc(shorter code and spares from having to find a name for the block variable), I think that as soon as more than one method is to be called inside the block, it's time to revert to the normal block syntax; in your example:%w(kung ruby bar).map { |word| word + "-fu" }.Yes, Roman, I'm inclined to agree; I've never put this into a "real" codebase, and this was an intellectual exercise to see how I'd want it to work. The fact that there are 3 very different implementations of Array#to_proc is a clear sign that there's no good "right" way.