Implicit return (last expression) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby method?

Consider this Ruby method. What will it return when called with calculate(5)?

Ruby

def calculate(x)
  y = x * 2
  y + 3
end

calculate(5)

A 10

B 8

C nil

D 13

💡 Hint

Remember, Ruby methods return the value of the last expression automatically.

The method multiplies 5 by 2 to get 10, then adds 3, so the last expression is 13, which is returned implicitly.

❓ Predict Output

intermediate

What does this Ruby method return?

Look at this method and tell what it returns when called with greet('Alice').

Ruby

def greet(name)
  message = "Hello, " + name
  message.upcase
end

greet('Alice')

A "HELLO, ALICE"

B "hello, alice"

C nil

D "Hello, Alice"

💡 Hint

The last expression is message.upcase, which changes the string to uppercase.

The method creates a greeting message and then returns the uppercase version of it because the last expression is message.upcase.

🔧 Debug

advanced

Why does this method return nil?

This method is supposed to return the doubled value of num, but it returns nil. Why?

Ruby

def double(num)
  result = num * 2
  puts result
end

double(4)

A Because <code>num</code> is not passed to the method

B Because <code>puts</code> returns nil and it is the last expression in the method

C Because <code>result</code> is not assigned correctly

D Because the method has no return statement

💡 Hint

Check what puts returns in Ruby.

In Ruby, puts outputs to the screen but returns nil. Since it's the last expression, the method returns nil.

🧠 Conceptual

advanced

What value does this method return?

Given this method, what is the return value when called with status_check(true)?

Ruby

def status_check(flag)
  if flag
    "Success"
  else
    "Failure"
  end
end

status_check(true)

A true

B "Failure"

C "Success"

D nil

💡 Hint

The last expression executed depends on the condition.

Since flag is true, the if branch returns "Success" as the last expression, so the method returns it.

❓ Predict Output

expert

What is the output of this Ruby code?

What does this method return when called with process(3)?

Ruby

def process(n)
  n.times do |i|
    return i if i == 2
  end
  10
end

process(3)

A 2

B 3

C 10

D nil

💡 Hint

The method uses an explicit return inside a loop.

The method returns 2 immediately when i == 2 inside the loop, so it never reaches 10.