Yield to execute blocks in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using yield?

Consider the following Ruby method that uses yield. What will be printed when this code runs?

Ruby

def greet
  puts "Hello"
  yield if block_given?
  puts "Goodbye"
end

greet { puts "How are you?" }

A Hello\nHow are you?\nGoodbye

B Hello\nGoodbye\nHow are you?

C How are you?\nHello\nGoodbye

D Hello\nGoodbye

💡 Hint

Remember that yield runs the block passed to the method exactly where it appears.

The method prints "Hello", then yields to the block which prints "How are you?", then prints "Goodbye".

🧠 Conceptual

intermediate

What does block_given? check in Ruby?

In Ruby, inside a method, what does the method block_given? return?

A True if a block was passed to the method, false otherwise

B True if the method has a yield statement, false otherwise

C True if the method returns a value, false otherwise

D True if the method is called with parentheses, false otherwise

💡 Hint

Think about how Ruby methods detect if a block was passed.

block_given? returns true only if the caller passed a block to the method.

🔧 Debug

advanced

Why does this Ruby code raise an error?

Look at this Ruby method and its call. Why does it raise a LocalJumpError?

Ruby

def run_block
  yield
  yield
end

run_block

A The method tries to yield twice, which is not allowed

B No block was given when calling <code>run_block</code>, so yield has nothing to execute

C The method is missing a return statement

D The block passed returns nil, causing an error

💡 Hint

What happens if you call yield but no block is given?

Calling yield without a block causes a LocalJumpError because Ruby doesn't know what to execute.

📝 Syntax

advanced

Which option correctly defines a method that yields to a block with a parameter?

You want to define a Ruby method that yields a value to a block. Which code is correct?

A

def example
  yield(10))
end

B

def example
  yield(10
end

C

def example
  yield 10 do
end

D

def example
  yield 10
end

💡 Hint

Check for correct parentheses and syntax around yield.

Option D correctly calls yield with an argument 10. Others have syntax errors like missing or extra parentheses.

🚀 Application

expert

What is the output of this Ruby code using yield with multiple yields and parameters?

Analyze this Ruby code and select the exact output it produces.

Ruby

def multi_yield
  yield(1)
  yield(2)
  yield(3)
end

result = []
multi_yield { |x| result << x * 2 }
puts result.join(",")

A 3,6,9

B 1,2,3

C 2,4,6

D Error: undefined method << for nil:NilClass

💡 Hint

The block doubles each yielded value and appends it to the array.

The method yields 1, 2, and 3. The block multiplies each by 2 and appends to result. Output is '2,4,6'.