4.5 Case Statements

Instead of using if-elsif statements, Ruby has another statement called case for handling multiple options. This statement is useful when presenting users with a large menu of different choices. The case statement is expressed in Example 4-11.

    1 case
    2 when (expression1)
    3 	# section 1
    4 when (expression2)
    5 	# section 2
    6 else
    7 	# section 3
    8 end

After looking at a case statement in use, you may be wondering what would happen if multiple when clauses evaluate to true. Case statements are processed in order, so the first condition that evaluates to true has its corresponding flow option execute, skipping over all others. As noted earlier, this processing order is identical to the cascaded if-else statements.

We now update the movie theater example, where children, adults, and senior citizens have differing rates to make use of the case statement as shown in Example 4-12.

     1 puts "Enter the customer's age: "
     2 # Get an integer age value from the user
     3 age = gets.to_i
     4 
     5 # Determine the cost based on age
     6 case
     7 when (age <= 12)
     8 	cost = 9
     9 when (age >= 65)
    10 	cost = 12
    11 else
    12 	cost = 18
    13 end
    14 
    15 # Print out the final cost
    16 puts "Ticket cost: " + cost.to_s