What does the "map" method do in Ruby?

Question

I'm new to programming. Can someone explain what `.map` would do in: params = (0...param_count).map

Answer 1

The map method in Ruby is a method that can be used with an array, hash, or range (an enumerable) to transform or change the data. Below are two examples of the syntax:

# Example #1 - Simple Example

# Here we use the map function to change the case of each

# item in this array from its curent form (uppercase) to lowercase

# array initialized

array = ["A", "B", "C"]

# map called on the array, each element is converted to lowercase

array.map! { |string| string.downcase }

# Using the ! operator in the above example is short for

# array = array.map (FYI)

# print to console screen

puts array

# Result is ["a", "b", "c"]

# -----------------------------------------------------------------

# Example #2 - Map with index

# You can also get the index of the array that is being operated on

# with the map.with_index

# array initialized

fruitArray = ["apple", "orange", "banana"]

# transform(modify) the array contents

fruitArray.map!.with_index { |element, index| [element, index] }

# print to console

puts fruitArray

#Result is: [ ["apple", 0], ["orange", 1], ["banana", 2] ]

Map is sometimes confused with the "each" method which is very similar to "map" however each returns the original unmodified version of the array. With the map function, you can change data and will have the modified array returned.

Another note to be aware of is that sometimes you might see a method called "collect" which is just an alias for map. Collect and map are the same exact method.