Ruby built-in method to yield self unless nil?

[Steve H]

I'm looking for something built-in to Ruby that works kind of like Object#tap, but only yields if self is not nil.

That is, can I do this without monkey-patching Object?

If it's in Activesupport that's fine too. I feel like this method exists but I can't find it.

class Object

  def tap_unless_nil

    if nil?

      nil

    else

      yield self

    end

  end

end

"hello".tap_unless_nil{ |a| puts "yielded #{a.inspect}" }

nil.tap_unless_nil{ |a| puts "yielded #{a.inspect}" }

[Ryan Bigg]

You can use Object#try from ActiveSupport to do this:

"hello".try(:tap) { |a| puts "yielded #{a.inspect}" }

nil.try(:tap) { |a| puts "yielded #{a.inspect}" }

try will attempt a method, but only if it's called on an object that's not nil.

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[Steve Hoeksema]

Aha! Didn't realise try could take a block. Thanks!

[Ryan Bigg]

try just takes all arguments to a method an passes them along, including blocks :)

[Ben Hoskings]

Well tap already does what you want for everything else, so:

class NilClass
def tap
nil
end
end

I'm not suggesting using this code... just pointing out that it's possible. :)

- Ben

[Ben Hoskings]

Also it's worth mentioning that code sample of yours won't do what you expect -- tap always returns its caller, but your method will return the block value for non-nil receivers.

The logic should be:

class Object
def tap_unless_nil
yield(self) unless nil?
self
end
end

Again, wouldn't endorse it, I'm just talkin' hypotheticals here :)

- Ben



On 14/06/2012, at 11:01 AM, Steve H wrote:

[Steve Hoeksema]

Cool, I wasn't actually using that code, just threw it together to illustrate what I was after. #try does what I want, so that's handy.