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redo and retry Statements in Ruby

Ruby redo and retry statements: In this tutorial, we are going to learn about the redo and retry statements with examples.
Submitted by Hrithik Chandra Prasad, on October 15, 2019

Ruby redo and retry statements

Ruby is a very flexible language; it provides you many ways through which you can make your code more effective and clear. With the help of redo and retry statement, you can make your code more readable to the user as well as you can perform functionalities more efficiently. Let us go through the syntax, area of implementation and example of each of the statements.

1) Ruby redo statement

redo statement comes into the scene when you have to re-execute the iteration in the same loop. It repeats the current iteration in the loop. The feature of the redo statement is that it executes without even evaluating the loop condition. Sometimes, this results in the creation of an infinite loop. Let us see the syntax and examples.

Syntax:

    while (#condition)
        #statements
        redo if  #condition
    end

Example 1:

=begin
Ruby program to demonstrate redo 
=end

i = 30   

while(i < 50)      
    puts "Value of i is #{i}"   
    i += 1   
    redo if i == 50
end   

Output

Value of i is 30
Value of i is 31
Value of i is 32
Value of i is 33
Value of i is 34
Value of i is 35
Value of i is 36
Value of i is 37
Value of i is 38
Value of i is 39
Value of i is 40
Value of i is 41
Value of i is 42
Value of i is 43
Value of i is 44
Value of i is 45
Value of i is 46
Value of i is 47
Value of i is 48
Value of i is 49
Value of i is 50

Explanation:

In the above code, you can see that the condition specified in the while loop tells the iteration to be done up to 49 but due to the introduction of redo statement the iteration is going up to 50 because redo statement executes before the condition is checked.

Example 2:

=begin
Ruby program to demonstrate redo 
=end

i = 30   

while(i < 50)      
    puts "Value of i is #{i}"   
    i += 1   
    redo if i > 45
end   

Output

An infinite loop

Explanation:

The above code will give an infinite loop because i will always be greater than 45.

2) Ruby retry statement

In Ruby, the retry statement only works inside the begin/rescue block. You can also say that it works in the context of exception handling. You should use a retry statement when you want to re-execute the block.

Syntax:

    retry

Example:

=begin
Ruby program to demonstrate retry 
=end

for i in 0..10
	begin
		puts "VALUE OF i #{i}"
		raise if i >=9
		rescue
		retry
	end
end

Output

Infinite loop.

Explanation:

This will also give an infinite loop because exception will be raised until i>=9 and this is an infinite situation.