Conditionals

Conditionals control the flow of execution of your program based on conditions that you define. Conditionals are the decision-making statements in your program.

If Statements

Decides if a block of code will be executed or not based on whether a condition is true.

age = 17

if (age >= 16)
  puts "You are eligible to get your driver's license."
end

# Output: You are eligible to get your driver's license.

If - Else Statements

If the condition in an if statement is false, the block of code in the else statement will be executed.

age = 15

if (age >= 16)
  puts "Can you drive me to the store?"
else
  puts "Can you walk with me to the store?"
end

# Output: Can you walk with me to the store?

If - Elseif - Else Statements

If the if statement is not true, the block of code in the elseif statement will be executed if the condition is true. There may me multiple elseif statements. Finally, if none of the conditions are true, the block of code in the else statement will be executed.

age1 = 35
age2 = 26
age3 = 19
age4 = 17
age5 = 15

def things_you_can_do(age)
  if (age >= 35)
    puts "You can run for president."
  elsif (age >= 25)
    puts "You can rent a car."
  elsif (age >= 18)
    puts "You can vote."
  elsif (age >= 16)
    puts "You can get a driver's license."
  else
    puts "You still have your youth!"
  end
end

things_you_can_do age1
things_you_can_do age2
things_you_can_do age3
things_you_can_do age4
things_you_can_do age5

# Output: You can run for president.
# Output: You can rent a car.
# Output: You can vote.
# Output: You can get a driver's license.
# Output: You still have your youth!

Ternary Statements

A shorter version of the if statement. It will evaluate an expression, if true, it will execute the code following the ?. If false, execute the code following the :.

# Example of condition evaluating to true
age1 = 19

can_vote = (age1 >= 18) ? "You can vote." : "You can't vote."

puts can_vote
# Output: You can vote.

# Example of condition evaluating to false
age2 = 17

can_vote = (age2 >= 18) ? "You can vote." : "You can't vote."

puts can_vote
# Output: You can't vote.