Yield to execute blocks in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to yield control to the block.

Ruby

def greet
  puts "Hello"
  [1]
  puts "Goodbye"
end

Drag options to blanks, or click blank then click option'

Areturn

Byield

Ccall

Dbreak

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'return' instead of 'yield' stops the method instead of calling the block.

Using 'call' without a block variable causes an error.

The keyword 'yield' passes control from the method to the block given to it.

2fill in blank

medium

Complete the code to pass a value to the block using yield.

Ruby

def square(number)
  [1] number * number
end

Drag options to blanks, or click blank then click option'

Ayield

Breturn

Cyield()

Dcall

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'return' instead of 'yield' does not call the block.

Using 'yield()' without argument does not pass the value.

Using 'yield' with an argument passes that argument to the block.

3fill in blank

hard

Fix the error in the method to correctly yield to the block with two arguments.

Ruby

def combine(a, b)
  [1] a, b
end

Drag options to blanks, or click blank then click option'

Ayield

Byield()

Cyield a, b

Dyield(a, b)

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'yield()' without arguments does not pass any values.

Using 'yield(a, b)' is invalid syntax in Ruby.

To pass multiple arguments to the block, use 'yield' followed by the arguments separated by commas.

4fill in blank

hard

Fill both blanks to create a method that yields the square of a number and then returns a string.

Ruby

def process(number)
  result = [1] number * number
  [2] "Done"
end

Drag options to blanks, or click blank then click option'

Ayield

Breturn

Cputs

Dyield()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'puts' instead of 'yield' does not call the block.

Not using 'return' causes the method to return the last evaluated expression.

The method yields the square to the block, then returns the string "Done".

5fill in blank

hard

Fill all three blanks to define a method that yields a greeting with a name, then yields a farewell, and finally returns a confirmation string.

Ruby

def conversation(name)
  [1] "Hello, #{name}!"
  [2] "Goodbye, #{name}!"
  [3] "Conversation finished"
end

Drag options to blanks, or click blank then click option'

Ayield

Breturn

Cyield()

Dputs

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'puts' instead of 'yield' does not call the block.

Using 'yield()' without arguments does not pass the messages.

The method yields two messages to the block and then returns a string.

Practice

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

easy

A. It runs the block of code passed to the method.

B. It returns the method's value immediately.

C. It defines a new method inside the current method.

D. It pauses the method execution permanently.

Solution

1. Step 1: Understand the role of yield

   The yield keyword is used inside a method to call the block that was passed to that method.

2. Step 2: Differentiate from other keywords

   Unlike return or method definitions, yield specifically executes the block given to the method.

3. Final Answer:

   It runs the block of code passed to the method. -> Option A

4. Quick Check:

   Yield executes block = A [OK]

Hint: Yield always runs the block given to the method [OK]

Common Mistakes:

• Thinking yield returns method value
• Confusing yield with return
• Assuming yield defines a method

2. Which of the following is the correct syntax to use yield with an argument inside a method?

easy

A. def example; yield(5); end

B. def example; yield5; end

C. def example; yield = 5; end

D. def example; yield: 5; end

Solution

1. Step 1: Recall yield syntax with arguments

   To pass arguments to the block, yield must be called with parentheses around the arguments, like yield(5).

2. Step 2: Check other options for syntax errors

   Options B, C, and D are incorrect because they either miss parentheses or use invalid syntax.

3. Final Answer:

   def example; yield(5); end -> Option A

4. Quick Check:

   Yield with args uses parentheses = A [OK]

Hint: Use parentheses to pass arguments with yield [OK]

Common Mistakes:

• Omitting parentheses when passing arguments
• Using assignment (=) with yield
• Using colon (:) instead of parentheses

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

def greet
  yield("Alice")
end

greet { |name| puts "Hello, #{name}!" }

medium

A. Error: no block given

B. Hello, Alice!

C. Hello, !

D. Hello, name!

Solution

1. Step 1: Understand yield with argument

   The method greet calls yield with the string "Alice" as argument, passing it to the block.

2. Step 2: Evaluate the block execution

   The block receives "Alice" as name and prints "Hello, Alice!".

3. Final Answer:

   Hello, Alice! -> Option B

4. Quick Check:

   Yield passes "Alice" to block = C [OK]

Hint: Yield passes arguments to block parameters [OK]

Common Mistakes:

• Ignoring the argument passed to yield
• Assuming block is not called
• Confusing variable names in block

4. Identify the error in the following Ruby code:

def run_block
  yield if block_given
end

run_block { puts "Block executed" }

medium

A. yield cannot be used without arguments

B. Syntax error in method definition

C. Block is not passed to the method

D. Missing question mark (?) in block_given? method call

Solution

1. Step 1: Check usage of block_given?

   The method to check if a block is given is block_given?, note the question mark.

2. Step 2: Identify the error in code

   The code uses block_given without the question mark (?), which causes a NameError because block_given is not a valid method.

3. Final Answer:

   Missing question mark (?) in block_given? method call -> Option D

4. Quick Check:

   Use block_given? with question mark [OK]

Hint: Always use block_given? (with ?) [OK]

Common Mistakes:

• Forgetting question mark (?) on block_given?
• Assuming yield needs arguments always
• Not passing a block when expected

5. Given the method below, what will be the output?

def repeat(n)
  if block_given?
    n.times { |i| yield(i) }
  else
    puts "No block given"
  end
end

repeat(3) { |num| puts num * 2 }

hard

A. 0
1
2

B. 1
2
3

C. 0
2
4

D. No block given

Solution

1. Step 1: Analyze the method behavior

   The method repeat checks if a block is given. Since a block is passed, it runs n.times and yields the index i to the block.

2. Step 2: Evaluate the block execution

   The block multiplies each yielded number by 2 and prints it. For n=3, i goes 0,1,2, so outputs are 0, 2, 4.

3. Final Answer:

   0 2 4 -> Option C

4. Quick Check:

   Yield with times and block multiplies index = D [OK]

Hint: Yield passes each index to block in times loop [OK]

Common Mistakes:

• Confusing index values starting at 1
• Ignoring block_given? check
• Expecting output without block