Passing multiple code blocks as arguments in Ruby

Question

I have a method which takes a code block.

def opportunity
  @opportunities += 1
  if yield
    @performances +=1
  end
end

and I call it like this:

opportunity { @some_array.empty? }

But how do I pass it more than one code block so that I could use yield twice, something like this:

def opportunity
  if yield_1
    @opportunities += 1
  end
  if yield_2
    @performances +=1
  end
end

and:

opportunity {@some_other_array.empty?} { @some_array.empty? }

I am aware that this example could be done without yield, but it's just to illustrate.

Arturo Herrero · Accepted Answer · 2015-01-24 21:34:20Z

73

You can't pass multiple blocks, per se, but you can pass multiple procs or lambdas:

Using 1.9 syntax:

opportunity ->{ @some_array.empty? }, ->{ @some_other_array.empty? }

and in the method itself:

def opportunity(lambda1, lambda2)
  if lambda1.()
    @opportunities += 1
  end
  if lambda2.()
    @performances += 1
  end
end

Arturo Herrero

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answered Mar 17, 2010 at 16:03

horseyguy

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4 Comments

Is it other way to declare that functions

Proc.new {} or lambda {} also work. Any object that responds to call will work

Is the method .() an alias of .call ?

@MrYoshiji YES! ruby-doc.org/core-2.2.0/Proc.html#method-i-call " Note that prc.() invokes prc.call() with the parameters given. It’s a syntax sugar to hide “call”."