Examining the following code
[1,2,3,4].map # => #<Enumerator: [1, 2, 3, 4]:map>
[1,2,3,4].each # => #<Enumerator: [1, 2, 3, 4]:each>
we can see that both are an enumerator. One is map and other is each. The method to_enum also returns an enumerator each. Is there any difference between these two enumerators?
Yes, when you iterate over the map enumerator, it will take the result and populate it into a new array:
[1,2,3,4].map.each { |n| n * 2 } # => [2, 4, 6, 8]
When you iterate over the each enumerator, it will return the original array
[1,2,3,4].each.each { |n| n * 2 } # => [1, 2, 3, 4]
Map exists to take an array of one type and convert it to an array of a different type, each exists to simply iterate over the array (doing something with a side effect for each element, such as printing it out).
