Conditional Statements

Last updated on June 30th, 2024 at 03:04 pm

Every programming language needs conditional statements to control the flow of logic.

Table of Contents

• If and Unless
• Conditional Statements
• Ternary Operator
• Case

If and Unless

As with just about every other language in existence, Ruby has the conditional statement if. Knowing how much Ruby loves positive statements, it also has the conditional statements unless which can basically be considered the negation of the if.

The if statement works as one would expect

if expression
  expression
elsif expression
  expression
else
  expression
end

The unless statement is similar to the if statement and simply negates the if logic, but does not (yet?) have an elsunless capability.

unless expression
  expression
else
  expression
end

One very interesting aspect of Ruby is that you can actually assign the if / unless statement and the last value in the execution block is assigned to the variable.

new_value = if expression
             expression
           elsif 
             expression
           else
             expression
           end

Conditional Statements

Ruby implements an interesting mechanism with conditionals. It allows you do execute an expression based upon whether or not the conditional is fulfilled.

var1 = "A string" if some_value_is_true
var2 = "A different string" unless some_value_is_false

Ternary Operator

Ruby implements a Ternary Operator similar to many other programming languages.

var = expression ? true-assignment : false-assigment

Case

Ruby also has a case statement, that works very much as one would expect. As with the if and unless, the results of the case can also be assigned.

case object
  when expression
    expression
  else
    expression
end

The case statement also has an “in” operator, which is hardly documented at all on the Internet. From what I have been able to find, it appears to check if the target value is in a collection.

a1 = [1,2,3,4,5]
a2 = [6,7,8,9,10]
case 1
in a1
  puts "in a1"
in a2
  puts "in a2"
end

For an interesting example of how the “in” operator works with JSON data, I suggest you have a look at a post by Brandon Weaver.

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