Block given? check in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using block_given??

Consider the following Ruby method that checks if a block is given and yields to it if so. What will be printed when calling greet with and without a block?

Ruby

def greet
  if block_given?
    yield
  else
    puts "No block given"
  end
end

greet

greet { puts "Hello from block!" }

A

No block given
No block given

B

No block given
Hello from block!

C

Hello from block!
No block given

D

Hello from block!
Hello from block!

💡 Hint

Remember that block_given? returns true only if a block is passed to the method.

The first call to greet has no block, so it prints "No block given". The second call has a block, so it yields and prints "Hello from block!".

🧠 Conceptual

intermediate

What does block_given? return inside a method?

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

A Raises an error if no block is given

B True if any method in the program has a block, false otherwise

C True if the method was called with a block, false otherwise

D Always true, because blocks are always available

💡 Hint

Think about whether the method itself received a block or not.

block_given? returns true only if the current method was called with a block.

🔧 Debug

advanced

Why does this code raise an error when using yield without block_given??

Look at this Ruby method:

def run
  yield
end

run

What error will this code raise and why?

A No error, it prints nothing

B NoMethodError because yield is not a method

C SyntaxError because yield is used incorrectly

D LocalJumpError because yield is called without a block

💡 Hint

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

Calling yield without a block causes a LocalJumpError because Ruby expects a block to execute.

❓ Predict Output

advanced

What is the output of this method using block_given? and yield?

What will this Ruby code print?

def check
  if block_given?
    yield(5)
  else
    puts "No block"
  end
end

check { |x| puts x * 2 }
check

A

10
No block

B

5
No block

C

No block
10

D

No block
No block

💡 Hint

The block receives the number 5 and multiplies it by 2.

The first call passes a block that prints 5 * 2 = 10. The second call has no block, so it prints "No block".

🧠 Conceptual

expert

How does block_given? behave with nested method calls?

Given these Ruby methods:

def outer
  inner
end

def inner
  block_given?
end

result = outer { puts "Hi" }

What is the value of result after this code runs?

A false

B true

C nil

D Raises an error

💡 Hint

Does the block passed to outer get passed automatically to inner?

The block is given to outer, but inner does not receive it unless explicitly passed. So block_given? inside inner returns false.