What's Up With #Map?

8/23/15

#Map, & #collect! They do... well, exactly the same thing. They map through an array, performing a function of your choice on every element, and then returning a block filled with all the new results. Map is more conventional than collect, so that's what we're going to talk about.

#Map is good for altering data by expanding on it: ie, doing math. If we need to add to, subtract from, multiply, or divide numbers in an array and we know we want to do it across the board, #map allows us to do this all at once:


      test_array = [2, 4, 6, 8, 10]
      test_array.map{|value| value*2 }
      => [4, 8, 12, 16, 20]

It looks a little bit like the .each / do command that we can call on a method, but used in the context of arrays (and also hashes!) Since we'll often need to modify data sets all at once, it's a useful, powerful tool.

And that's all she wrote today! I hope that was helpful!