|map|
Ruby's #map is an extremely useful upgrade from using #each. Not only is it less code to write but it also looks much cleaner. Check out these examples of what #map can do in the place of #each.
rainbow = ["red", "orange", "yellow", "green", "blue", "purple"]
colors = []
rainbow.each{ |color| colors << color.upcase }
colors
# returns ["RED", "ORANGE", "YELLOW", "GREEN", "BLUE", "PURPLE"]
rainbow.map{ |color| color.upcase }
# returns ["RED", "ORANGE", "YELLOW", "GREEN", "BLUE", "PURPLE"]
Pretty cool right! Ruby's #map returns a new array without changing the original one. If you were to use #each you would need to create an empty array to shovel or push the altered values into. You can use map to grab all of the things!
|select|
What if you just wanted to grab specific things instead of mapping all of the things? Well you actually can with #select!
colors = []
rainbow.each do |color|
if color.length > 5
colors << color
end
end
colors
# returns ["orange", "yellow", "purple"]
rainbow.select{ |color| color.length > 5 }
# returns ["orange", "yellow", "purple"]
In this example we only grab colors with a length greater than 5. When using
#selecta new array will be created and populated with the values we specify.
|max_by|
What if you want to grab the largest thing? You can use #max_by to grab the max value of something.
rainbow = ["red", "orange", "yellow", "green", "blue", "purpleee"]
longest = ""
rainbow.each do |color|
if color.length > longest.length
longest = color
end
end
longest
# returns "purpleee"
rainbow.max_by{ |color| color.length }
# returns "purpleee"
You can also specify how many values you want returned. The values returned are similar to using #sample so the order will be random.
rainbow = ["red", "orange", "yellow", "green", "blue", "purple"]
colors = []
longest = ""
second_longest = ""
third_longest = ""
rainbow.each do |color|
if color.length >= longest.length
third_longest = second_longest
second_longest = longest
longest = color
end
end
colors.push(longest, second_longest, third_longest)
colors
# returns ["purple", "orange", "yellow"]
rainbow.max_by(3){ |color| color.length }
# returns ["purple", "orange", "yellow"]
If our array looked like this
["red", "orange", "yellow", "greenn", "blue", "purple"]then any combination of 3 of these["yellow", "greenn", "orange", "purple"]could have been returned.
|include?|
What if we wanted to find out if our rainbow array has a certain color? We can do that by using #include?.
rainbow.each do |color|
if color == "purple"
true
else
false
end
end
# returns true
rainbow.include?("purple")
# returns true
rainbow.include?("pink")
# returns false
Keep in mind that
include?returns true or false and not a new array.
The magic of & with enumerables.
We can even use this shorthand with enumerables when we don't need to pass in any arguments. This really blew my mind when I found out about it.
rainbow.map(&:upcase)
# take note that the usual squigglys{} are now parentheses().
# returns ["RED", "ORANGE", "YELLOW", "GREEN", "BLUE", "PURPLE"]
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