Write One Line if Statement in Ruby

  2. HowTo
  3. Ruby Howtos
  4. Write One Line if Statement in Ruby
Nurudeen Ibrahim Sep 15, 2023 Feb 07, 2022
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
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 = if number.even? then "Yeah, it's even" else "No, it's not" end
  # 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 unless !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 = unless number.even? then "No, it's not" else "Yeah, it's even" end
  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:

if condition then true_expression else false_expression end

Sample Code:

grade = 85
if grade >= 70 then puts "Pass" else "Fail" end

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:

if condition then (true_expression) else (false_expression) end

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 = case
         when condition1 then expression1
         when condition2 then expression2
         else default_expression
         end

Sample Code:

number = 7
result = case
         when number < 0 then "Negative"
         when number == 0 then "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.