What will we do if we want to execute code only in a specific condition? The conditional statements help us here. Lets take an example, I want to check if a number is in range 0 to 100 or not.
If statement
This check a condition and if condition is true then executes the code inside it.
- print 'give a number: '
- # take a number from user
- # execute this code and write a number
- a = gets.to_i
-
- # check condition
- if a < 100
- puts 'a is less than 100'
- end
If else statement
This check a condition and if condition is true then execute the code inside it otherwise execute the code inside the else statement.
- print 'give a number: '
- # take a number from user
- # execute this code and write a number
- a = gets.to_i
-
- # check condition
- if a < 100 and a >0
- puts 'a is between 0 and 100'
- else
- # code inside else statement
- puts 'a is outside the range'
- end
If and elsif statement:
This statement check one condition if condition is false then check condition of elsif and it condition is true then run code inside that statement otherwise continue to next condition.
- print 'give a number: '
- # take a number from user
- # execute this code and write a number
- a = gets.to_i
-
- # if condition
- if a < 100 and a > 0
- puts 'a is between 0 and 100'
- # elsif condition
- elsif a<1000
- puts 'a is less than 1000'
- # statement can has multiple elsif statement
- # finally else statement
- else
- puts 'a is out of range'
- end
If modifier:
This is modified one line if statement. Syntax is => code if condition
- print 'give a number: '
- # take an integer from user
- # execute this code and write a number
- a = gets.to_i
-
- # if modifier statement
- puts 'a is less than 100' if a<100
Ruby unless statement:
This is opposite to the if statement. The code inside this statement executes when condition is false. You can assume it as an if statement with opposite condition.
- print 'give a number: '
- # take an integer from user
- # execute this code and write a number
- a = gets.to_i
-
- # unless statement
- unless a>= 100
- puts 'a is less than 100'
- end
Ruby unless modifier:
This is modified one line unless statement.
- print 'give a number: '
- # take an integer from user
- # execute this code and write a number
- a = gets.to_i
-
- # modified unless statement
- puts 'a is less than 100' unless a>= 100
Ruby case statement:
Case statement is a modified if elsif statement, in which we take a data value and compare that value with a number of cases.
- print 'give a number: '
- # take an integer from user
- # execute this code and write a number
- a = gets.to_i
-
- # take a data value using keyword case
- case a
- # check conditions => 1..99 means in the range of 1 to 99
- when 1..99
- puts 'a is between 0 and 100'
- # check from 100 to 1000
- when 100..1000
- puts 'a is between 99 and 1000'
- # if above two cases fail then use else statement
- else
- puts 'a is outside the range'
- # close case using end keyword
- end
