Types of Ruby Iterators

Richard Chea
1 min readDec 21, 2020

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In Ruby, arrays and hashes are collections. Then there are iterators, which are methods that can be used on a collection. We will look at a few of these iterators in this post.

.each

The each method doesn’t modify the original collection and will always return the original collection.

pizza_toppings = [“cheese”, “pineapple”, “pepperoni”]pizza_toppings.each do |topping|
puts “I want #{topping} on my pizza.”
end

In the block of code above, we have a puts with a string and will print out each line with the topping.

I want cheese on my pizza.
I want pineapple on my pizza.
I want pepperoni on my pizza.

The return value is below.

=> [“cheese”, “pineapple”, “pepperoni”]

.map

The map method will return a modified version of the collection without modifying the original collection.

pizza_toppings = [“cheese”, “pineapple”, “pepperoni”]pizza_toppings.map do |topping|
“I want #{topping} on my pizza.”
end

The return value is below.

=> [“I want cheese on my pizza.”, “I want pineapple on my pizza.”, “I want pepperoni on my pizza.”]

Don’t forget that the original collection stays the same.

pizza_toppings
=> [“cheese”, “pineapple”, “pepperoni”]

.select

The select method is used to iterate through the collection and select the ones that evaluate to true.

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]numbers.select do |number|
number.even?
end
=> [2, 4, 6, 8, 10]

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