How to Write One Line if Statement in Ruby

Nurudeen Ibrahim Feb 02, 2024 Ruby Ruby Condition Ruby Operators
  1. Write a One-Line Statement Using the Ternary Operator in Ruby
  2. Write a One-Line Statement Using IF Only in Ruby
  3. Write a One-Line Statement Using if-else in Ruby
  4. Write a One-Line Statement Using unless in Ruby
  5. Write a One-Line Statement Using unless-else in Ruby
  6. Write a One-Line Statement Using if-else with then
  7. Write a One-Line Statement Using if-else with Parentheses
  8. Write a One-Line Statement Using case for Multiple Conditions
How to Write One Line if Statement in Ruby

Ruby, known for its elegant and concise syntax, provides multiple ways to write one-line if statements.

In this article, we’ll discuss six methods for writing one-line if statements in Ruby.

Write a One-Line Statement Using the Ternary Operator in Ruby

The usage of the ternary operator is similar to how it’s used in other programming languages.

Syntax:

condition ? do_something_if_condition_is_true : do_another_thing_if_condition_is_false

Example Code:

# Define a function named 'check_even' that takes a number as an argument.
def check_even(number)
  # Use a ternary operator to determine if the number is even or not, and store the result in 'response'.
  response = number.even? ? "Yeah, it's even" : "No, it's not"

  # Output the 'response' to the console.
  puts response
end

# Call the 'check_even' function to check if it's even.
check_even(4)
check_even(5)

Output:

Yeah, it's even
No, it's not

Write a One-Line Statement Using IF Only in Ruby

This is useful when you want to do something only if a condition is true and do nothing if the condition is false.

Example Code:

# Define a function named 'increment_with_even' that takes an argument 'n'.
def increment_with_even(n)
  # Initialize a variable 'number' with the value 10.
  number = 10
  # If 'n' is even, increment 'number' by 'n'.
  number += n if n.even?
  # Output the value of 'number' to the console.
  puts number
end

# Call the 'increment_with_even' function with the arguments 4 and 5.
increment_with_even(4)
increment_with_even(5)

Output:

14
10

Write a One-Line Statement Using if-else in Ruby

This is a regular if-else where you specify an action if a condition is true and another action if it’s false.

Example Code:

# Define a function named 'check_even' that takes a 'number' as an argument.
def check_even(number)
  # Use a conditional statement to assign 'response' based on whether 'number' is even or not.
  response = number.even? ? "Yeah, it's even" : "No, it's not"
  # Output the 'response' to the console.
  puts response
end

# Call the 'check_even' function with the arguments 4 and 5 to check if it's even.
check_even(4)
check_even(5)

Output:

Yeah, it's even
No, it's not

Write a One-Line Statement Using unless in Ruby

The unless is the opposite form of if. It means if not.

# Define a function named 'increment_with_even' that takes an argument 'n'.
def increment_with_even(n)
  # Initialize a variable 'number' with the value 10.
  number = 10
  # Increment 'number' by 'n' if 'n' is even (unless 'n' is not even).
  number += n if n.even?
  # Output the value of 'number' to the console.
  puts number
end

# Call the 'increment_with_even' function with the arguments 4 and 5.
increment_with_even(4)
increment_with_even(5)

Output:

14
10

The usage of unless in the above example is not recommended. Use this way for illustration.

The unless is seen as a negative statement. In this case, it should not be used on a negative expression !n.even?, making code more difficult to understand.

Write a One-Line Statement Using unless-else in Ruby

def check_even(number)
  response = number.even? ? "Yeah, it's even" : "No, it's not"
  puts response
end

check_even(4)
check_even(5)

Output:

Yeah, it's even
No, it's not

Write a One-Line Statement Using if-else with then

You can also use the then keyword to create a one-line if-else statement.

Syntax:

condition ? true_expression : false_expression

Sample Code:

grade = 85
grade >= 70 ? (puts 'Pass') : 'Fail'

Output:

Pass

In this code, the condition grade >= 70 is checked, and if it’s true, the true expression "Pass" is executed; otherwise, the false expression "Fail" is executed.

Write a One-Line Statement Using if-else with Parentheses

You can wrap the expressions in parentheses for clarity in a one-line if-else statement.

Syntax:

condition ? true_expression : false_expression

Sample Code:

x = 10
puts x > 5 ? 'x is greater than 5' : 'x is not greater than 5'

Output:

x is greater than 5

This code checks if x is greater than 5 and prints the corresponding message accordingly.

Write a One-Line Statement Using case for Multiple Conditions

You can use the case statement for concise one-liners when you have multiple conditions to check.

Syntax:

result = if condition1
           expression1
         elsif condition2
           expression2
         else
           default_expression
         end

Sample Code:

number = 7
result = if number < 0
           'Negative'
         elsif number == 0
           'Zero'
         else
           'Positive'
         end
puts result

Output:

Positive

In this example, the number is checked against multiple conditions, and the corresponding result is stored in the result variable.

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