Ruby Language Iteration Each
Example
Ruby has many types of enumerators but the first and most simple type of enumerator to start with is each. We will print out even or odd for each number between 1 and 10 to show how each works.
Basically there are two ways to pass so called blocks. A block is a piece of code being passed which will be executed by the method which is called. The each method takes a block which it calls for every element of the collection of objects it was called on.
There are two ways to pass a block to a method:
Method 1: Inline
(1..10).each { |i| puts i.even? ? 'even' : 'odd' }
This is a very compressed and ruby way to solve this. Let's break this down piece by piece.
(1..10)is a range from1to10inclusive. If we wanted it to be1to10exclusive, we would write(1...10)..eachis an enumerator that enumerates overeachelement in the object it is acting on. In this case, it acts oneachnumber in the range.{ |i| puts i.even? ? 'even' : 'odd' }is the block for theeachstatement, which itself can be broken down further.|i|this means that each element in the range is represented within the block by the identifieri.putsis an output method in Ruby that has an automatic line break after each time it prints. (We can useprintif we don't want the automatic line break)i.even?checks ifiis even. We could have also usedi % 2 == 0; however, it is preferable to use built in methods.? "even" : "odd"this is ruby's ternary operator. The way a ternary operator is constructed isexpression ? a : b. This is short for
if expression a else b end
For code longer than one line the block should be passed as a multiline block.
Method 2: Multiline
(1..10).each do |i|
if i.even?
puts 'even'
else
puts 'odd'
end
end
In a multiline block the do replaces the opening bracket and end replaces the closing bracket from the inline style.
Ruby supports reverse_each as well. It will iterate the array backwards.
@arr = [1,2,3,4]
puts @arr.inspect # output is [1,2,3,4]
print "Reversed array elements["
@arr.reverse_each do |val|
print " #{val} " # output is 4 3 2 1
end
print "]\n"
