jordansissel/tutorial.md

## tutorial.md

      
    Raw
  

              tutorial.md
            
          
    Example usage of the '&:foo' syntax
# You can do this:
p ["hello", "world"].collect(&:upcase)

Output:
["HELLO", "WORLD"]

What just happeend? What does '&:upcase' mean?
We can see that it called "hello".upcase, etc, for each element in the array.
What really is goign on though? We can play with it by capturing the proc generated by '&:upcase':
def getmethod(&block)
  return block
end

func = getmethod(&:upcase)
p func

output (from irb):
#<Proc:0x00007fe1ab12ad60@(irb):29>

What can we do with that:
func.call("hello there!")

Output:
"HELLO THERE!"

So passing &:foo to a method as the 'block' seems to generate a method that calls the 'foo' method on the first argument.
And that is exactly what .collect(&:upcase) does in the example at the top.