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Ruby - For Loop



The for loop executes a set of statements in each iteration. Whenever, number of iteration is known, for loop is preferred over while loop. A for loop expression is separated from code by the reserved word do, a newline, or a semicolon.

Syntax

for variable [, variable ...] in expression [do]
  statements
end

Example:

In the example below, the program continue to print variable called i from value 1 to 5. After that, it exits from the for loop.

for i in 1..5 do
  puts "Value of i = #{i}" 
end

The output of the above code will be:

Value of i = 1
Value of i = 2
Value of i = 3
Value of i = 4
Value of i = 5

Example: for loop over an array

A for loop can be used to access elements of an array. Consider the example below:

MyStr = ["Red", "Blue", "Green"]

for i in MyStr do
  puts i
end

The output of the above code will be:

Red
Blue
Green

A for..in loop is almost equivalent to the each iterator used with sequence created using range operator.

#method 1
(expression).each do |variable|
  statements
end

#method 2
(expression).each { |variable|
  statements
}

Example:

In the example below, the each iterator is used like a for loop.

#using each iterator like a for loop
(5..10).each do |i|
  puts "Value of i = #{i}"
end

The output of the above code will be:

Value of i = 5
Value of i = 6
Value of i = 7
Value of i = 8
Value of i = 9
Value of i = 10

5