Block syntax (do..end and curly braces) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of block with do..end vs curly braces

What is the output of the following Ruby code?

Ruby

def test_block
  yield
end

result = []
test_block do
  result << 1
end

test_block { result << 2 }

puts result.inspect

A [1, 2]

B [2, 1]

C SyntaxError

D []

💡 Hint

Both do..end and curly braces can be used to pass blocks to methods.

Both blocks add elements to the same array in order: first 1, then 2.

❓ Predict Output

intermediate

Return value of block with do..end vs curly braces

What is the output of this Ruby code?

Ruby

def block_return
  result = yield
  puts result
end

block_return do
  5 + 3
end

block_return { 10 + 2 }

A SyntaxError

B

nil
nil

C

5
10

D

8
12

💡 Hint

The yield keyword returns the value of the block.

The block returns 8 and 12 respectively, which are printed by puts.

🔧 Debug

advanced

Identify the syntax error in block usage

Which option contains a syntax error when defining a block in Ruby?

A array.map { |x| x * 2 }

B array.map { |x| x * 2 end }

C array.map do |x|; x * 2; end

D array.map do |x| x * 2 end

💡 Hint

Check if the block delimiters match correctly.

Option B mixes curly braces and do..end incorrectly, causing a syntax error.

🧠 Conceptual

advanced

Difference in precedence between do..end and curly braces

Which statement about Ruby block syntax precedence is true?

A Both have the same precedence

B do..end blocks have higher precedence than curly braces

C Curly braces have higher precedence than do..end blocks

D Precedence depends on the method name

💡 Hint

Think about how Ruby parses method calls with blocks.

Curly braces bind more tightly to the method call than do..end blocks, affecting how arguments are parsed.

🚀 Application

expert

Predict output with nested blocks and different syntax

What is the output of this Ruby code?

Ruby

def outer
  yield
end

outer do
  outer { puts 'Inner block' }
  puts 'Outer block'
end

A

Inner block
Outer block

B Inner block

C SyntaxError

D

Outer block
Inner block

💡 Hint

Blocks can be nested and execute in order of yield calls.

The inner block prints first because it is yielded inside the outer block before printing 'Outer block'.