Ruby Iterators

Iterators are Ruby methods that are called on collections, that is hashes, arrays, etc. A loop runs a block of code for a certain number of times while an iterator run a block of code on a data set.

You’d call an iterator on a collection when you want to run some logic on each element of said collection and return a value.

Ruby iterators are chainable, just like most Ruby methods.

each

array = [ 1, 2, 3]
array.each do |num|
   puts num + 5
end
# 6
# 7
# 8

you can also define and call the iterator in one step

[ 1, 2, 3].each do |num|
   puts num + 5
end
# 6
# 7
# 8

The each iterator returns all elements in a collection after running a block of code on them.

collect

array_one = [ 1, 2, 3]
array_two = Array.new
array_two = array_one.collect
puts array_two
# 1
# 2
# 3

The collect iterator returns all elements of a collection after running a block of code on each element.

collect/map

array = [1, 2, 3]
array.map do |element|
   element + 1
end
# [2, 3, 4]
array
# [1, 2, 3]

You can use map or collect, different names but they’re the same thing, I prefer map but you do you.

The difference between each and map, is that map returns a new object. That is deal when you don’t want to modify the original object but create a new one instead. If you add an exclamation sign ! it’ll overwrite the original array so use with care.

times

3.times do
   puts 'hello World'
end
# Hello World
# Hello World
# Hello World
3.times do |num|
   puts 'hello World ' + num + '.'
end
# Hello World 0.
# Hello World 1.
# Hello World 2.

Times is super simple, it repeats a block of code a certain number of times and you can even pass it a parameter to access the ‘time’ it’s running.

select and find

array = [1, 2, 3, 4, 5]
array.select do |element|
   element.odd?
end
# [1, 3, 5]

Select will ‘select’ all the elements that meet a certain criteria, in this case it’ll pick all the odd numbers. Find has a similar syntax but it will only return the first element that meets the criteria.

all? and any?

array = [1, 2, 3, 4, 5]
array.all? do |element|
   element.odd?
end
# false
array = [1, 2, 3, 4, 5]
array.any? do |element|
   element.odd?
end
# true

Both these methods return a boolean value if the search criteria is met. All? will return true when all the elements meet the criteria while any? returns true if any of the elements meet it.

I hope this little article helped you get an idea on how to use Ruby iterators and the simple syntax needed to make them run. Happy coding!