From: Emeka Patrick <lists@...>
Date: 2012-06-28T07:52:15+09:00
Subject: Using Yield - Lambdas & Blocks exercise Ruby Monk

Hi,

New to Ruby and currently trying to get a grasp of Lambdas and Blocks.
I've been able to understand basic uses of yield,  I was stuck on this
problem in RubyMonk this problem in section 7.2, but finally came up
with the answer below. However, I must admit that I'm not sure if I've
fully grasped or explained adequately why the answer works, but I made
some comments on it.

Could someone review the code and offer some advice / help?

Thanks,

Emeka


Problem:

class Array
  def transmogrify # see? no 'fn' parameter. magic.
    result = []
    each do |pair|
      # how do you think 'yield' will be used here?
    end
    result
  end
end

def names
  [["Christopher", "Alexander"],
   ["John", "McCarthy"],
   ["Joshua", "Norton"]].transmogrify do |pair|
      # by passing the entire element, we give more control to the block
  end
end


My answer:

class Array
  def transmogrify # define method transmogrify
    result = [] # opens empty array called result
    each do |pair| # calls block once for each element in object
    result << yield(pair) # passes variable 'pair' to yield
# returns modified block of code
# pushes it to the array named 'result'
end
result # calls up array named 'result'
  end
end


def names # define method called 'names'
  [["Christopher", "Alexander"],
   ["John", "McCarthy"],
   ["Joshua", "Norton"]].transmogrify do |pair| # calls method
# transmogrify on given array
   "#{pair[0]} #{pair[1]}" # passes elements in array through block of
# code which takes each pair of elements in nested array and
# combines into a single string
end
end

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