Explicit return statement in Ruby - Mini Project: Build & Apply

Explicit return statement

📖 Scenario: You are creating a simple calculator function that adds two numbers. You want to make sure the function clearly returns the result using an explicit return statement.

🎯 Goal: Build a Ruby method called add_numbers that takes two numbers as input and returns their sum using an explicit return statement.

📋 What You'll Learn

Create a method named add_numbers with two parameters: a and b

Inside the method, use an explicit return statement to return the sum of a and b

Call the method with the numbers 5 and 7 and store the result in a variable called result

Print the value of result

💡 Why This Matters

🌍 Real World

Explicit return statements make your code clear and easy to understand, especially when working with functions that perform calculations or data processing.

💼 Career

Many programming jobs require writing clear functions that return values explicitly, which helps with debugging and maintaining code.

1

Create the method skeleton

Write a method named add_numbers that takes two parameters called a and b. Leave the method body empty for now.

Ruby

def add_numbers(a, b)
  # Your code here
end

Hint

Use def to start the method and end to finish it.

2

Add explicit return statement

Inside the add_numbers method, write an explicit return statement that returns the sum of a and b.

Ruby

def add_numbers(a, b)
  # Your code here
end

Hint

Use return a + b to return the sum explicitly.

3

Call the method and store result

Call the add_numbers method with arguments 5 and 7, and store the result in a variable called result.

Ruby

def add_numbers(a, b)
  return a + b
end

# Your code here

Hint

Assign the method call add_numbers(5, 7) to result.

4

Print the result

Print the value of the variable result to display the sum.

Ruby

def add_numbers(a, b)
  return a + b
end

result = add_numbers(5, 7)

# Your code here

Hint

Use puts result to print the sum.

Practice

1. What does the return keyword do in a Ruby method?

easy

A. It prints a value to the screen.

B. It immediately sends a value back and stops the method.

C. It creates a new variable inside the method.

D. It pauses the method without returning a value.

Solution

1. Step 1: Understand the purpose of return

   The return keyword in Ruby is used to send a value back from a method immediately.

2. Step 2: Recognize method behavior with return

   When Ruby sees return, it stops running the method and gives back the specified value.

3. Final Answer:

   It immediately sends a value back and stops the method. -> Option B

4. Quick Check:

   Explicit return stops method and returns value = B [OK]

Hint: Return sends value back and stops method immediately [OK]

Common Mistakes:

• Thinking return prints output
• Confusing return with variable creation
• Believing return pauses without returning

2. Which of the following is the correct way to explicitly return the value 10 from a Ruby method?

easy

A. return10

B. return = 10

C. return: 10

D. return(10)

Solution

1. Step 1: Check Ruby syntax for return

   Ruby allows return with or without parentheses, so return(10) is correct syntax.

2. Step 2: Identify invalid options

   return10 lacks space (syntax error), return = 10 is invalid assignment, and return: 10 uses wrong colon syntax.

3. Final Answer:

   return(10) -> Option D

4. Quick Check:

   Correct explicit return syntax = C [OK]

Hint: Use return with parentheses for explicit clarity [OK]

Common Mistakes:

• Using assignment syntax with return
• Using colon instead of parentheses
• Omitting parentheses but expecting error

3. What will be the output of this Ruby code?

def example
  return 5
  10
end

puts example

medium

A. 5

B. 10

C. nil

D. SyntaxError

Solution

1. Step 1: Analyze the method example

   The method first executes return 5, which immediately stops the method and returns 5.

2. Step 2: Understand unreachable code

   The line 10 after the return is never reached or executed.

3. Final Answer:

   5 -> Option A

4. Quick Check:

   Return stops method early, output = 5 [OK]

Hint: Return stops method; code after return is ignored [OK]

Common Mistakes:

• Thinking code after return runs
• Expecting last line value as output
• Confusing return with print

4. Identify the error in this Ruby method:

def check_number(num)
  if num > 0
    return 'Positive'
  else
    'Negative'
  end
  return
end

medium

A. The method has unreachable code after return.

B. The return keyword is used incorrectly inside if.

C. The else block should use return explicitly.

D. The method returns nil for negative numbers.

Solution

1. Step 1: Trace the if branch

   If num > 0, return 'Positive' exits the method immediately.

2. Step 2: Trace the else branch

   Else block evaluates 'Negative' as last expression (implicit return).

3. Step 3: Check post-conditional code

   The final return (nil) is unreachable as if-else covers all paths.

4. Final Answer:

   The method has unreachable code after return. -> Option A

5. Quick Check:

   Complete if-else leads to unreachable code [OK]

Hint: Check all paths return a value explicitly [OK]

Common Mistakes:

• Assuming last return runs always
• Thinking return inside if is wrong
• Ignoring implicit returns

5. You want a method that returns the first even number from an array or nil if none found. Which code correctly uses explicit return to stop early?

def first_even(numbers)
  numbers.each do |n|
    if n.even?
      return n
    end
  end
  nil
end

hard

A. Returns nil always because return is inside loop.

B. Returns all even numbers as an array.

C. Returns first even number or nil, stops early with return.

D. Raises error because return cannot be used in block.

Solution

1. Step 1: Understand method logic

   The method loops over each number and checks if it is even.

2. Step 2: Analyze explicit return usage

   When it finds an even number, it uses return n to immediately return that number and stop the method.

3. Step 3: Check fallback return

   If no even number is found, the method returns nil after the loop.

4. Final Answer:

   Returns first even number or nil, stops early with return. -> Option C

5. Quick Check:

   Explicit return stops loop and returns value early = A [OK]

Hint: Use return inside loop to exit method early when condition met [OK]

Common Mistakes:

• Thinking return inside block causes error
• Expecting all even numbers returned
• Ignoring nil fallback return