In this post, we will have a look on various type of looping constructs in Ruby.
Let us check them one by one with examples:
1. While Loop
While loop executes till the condition is true.
Syntax
while condition do end
Example:
i = 1
n = 5
while i <= 10 do
puts("%d * %d = %d" % [i, n, i*n])
i +=1
end
2. Begin While Loop
This loop executes its statements first and then checks the condition
Syntax
begin end while condition
Example
n = 1
begin
puts("n = %d" % n )
n +=1
end while n%5!=0
3. For Loop
This loop executes till the loop counter variable is in the provided range. In the example below, i is the loop counter variable. The initial value of i is 1 and it the loop will execute till value of i is less than or equal to 10.
Syntax
for variable in range end
Example
n = 5
for i in 1..10
puts("%d * %d = %d" % [i, n, i*n])
end
4. Until Loop
This loop executes its code while condition is false.
Syntax
until condition do end
Example
n = 5
until n < 1 do
puts("n = %d" % n )
n -=1
end
5. Begin Until Loop
This loop executes its statement first and then checks the condition. It runs till condition is false.
Syntax
begin end until n < 1
Example
n = 5
begin
puts("n = %d" % n )
n -=1
end until n < 1
6. Each Loop
This loop executes its statement first and then checks the condition. It runs till condition is false.
Syntax
(range).each do |variable| end
Example
n = 5
(1..10).each do |i|
puts("%d * %d = %d" % [i, n, i*n])
end
Reverse order loop is a bit typical in Ruby. Here is an example:
n = 5
range = 10..1
(range.first).downto(range.last).each do |i|
puts("%d * %d = %d" % [i, n, i*n])
end
Breaking the loop
We can stop the execution of a loop in the middle with the help of break statement. Here is an example:
n = 1
begin
puts("n = %d" % n )
n +=1
if n>5 then
break
end
end while n%10!=0
Skipping loop statements
We can skip rest of the loop and jump to next iteration with the help of next. Here is an example:
n = 5
(1..10).each do |i|
if i%2==0 then
next
end
puts("%d * %d = %d" % [i, n, i*n])
n -=1
end
Re-starting loop
We can reset a loop to start from beginning. Here is an example:
n = 1
while n <= 5
for i in 1..10
puts("%d * %d = %d" % [n, i, n*i])
end
puts("-----------------------")
n += 1
if n>5 then
print("View again? y/n : ")
choice = gets().strip() #strip removes white space characters
if choice == "y" then
redo
end
end
end