Variable-length arguments (*args) in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method that accepts any number of arguments.

Ruby

def greet([1])
  puts "Hello, #{args.join(', ')}!"
end

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

A*args

B&args

Cargs

D**args

Attempts:

3 left

💡 Hint

Common Mistakes

Using &args instead of *args, which is for blocks.

Using **args which is for keyword arguments.

Not using any symbol, which only accepts one argument.

Using *args allows the method to accept any number of arguments as an array.

2fill in blank

medium

Complete the code to call the method with multiple arguments.

Ruby

greet([1])

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

A"Alice", "Bob", "Carol"

B"Alice"

C["Alice", "Bob"]

D:Alice, :Bob

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an array instead of separate arguments.

Passing symbols instead of strings.

Passing only one argument when multiple are needed.

Passing multiple arguments separated by commas matches the *args parameter.

3fill in blank

hard

Fix the error in the method definition to correctly accept variable arguments.

Ruby

def sum_numbers([1])
  sum = 0
  args.each { |num| sum += num }
  sum
end

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

A&args

Bargs

C*args

D**args

Attempts:

3 left

💡 Hint

Common Mistakes

Using args without * causes an error because it expects one argument.

Using &args is for blocks, not variable arguments.

Using **args is for keyword arguments.

The method must use *args to accept variable-length arguments as an array.

4fill in blank

hard

Fill both blanks to create a method that sums only positive numbers from variable arguments.

Ruby

def sum_positive([1])
  args.select { |n| n [2] 0 }.sum
end

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

A*args

B>

C>=

Dargs

Attempts:

3 left

💡 Hint

Common Mistakes

Using args without * causes errors.

Using >= includes zero, which is not positive.

Using < or <= selects negative or zero numbers.

*args collects all arguments, and > filters positive numbers.

5fill in blank

hard

Fill all three blanks to define a method that prints each argument with its index.

Ruby

def print_args([1])
  args.each_with_index do |[2], [3]|
    puts "#{index}: #{arg}"
  end
end

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

A*args

Barg

Cindex

Dargs

Attempts:

3 left

💡 Hint

Common Mistakes

Using args without * causes errors.

Swapping the order of block variables.

Using wrong variable names in the block.

*args collects arguments, and each_with_index provides each argument and its index.

Practice

1. What does *args do in a Ruby method?

easy

A. Makes the method return an array

B. Restricts the method to accept only one argument

C. Converts all arguments to strings automatically

D. Allows the method to accept any number of arguments as an array

Solution

1. Step 1: Understand the role of *args

   *args collects all extra arguments passed to a method into an array.

2. Step 2: Recognize the flexibility it provides

   This lets the method accept any number of arguments, not just one fixed number.

3. Final Answer:

   Allows the method to accept any number of arguments as an array -> Option D

4. Quick Check:

   *args = variable number of arguments [OK]

Hint: Remember *args packs all extra inputs into an array [OK]

Common Mistakes:

• Thinking *args limits arguments to one
• Confusing *args with return values
• Assuming *args converts types automatically

2. Which of the following is the correct syntax to define a method that accepts variable-length arguments in Ruby?

easy

A. def example(args*)

B. def example(args)

C. def example(*args)

D. def example(&args)

Solution

1. Step 1: Identify the correct syntax for variable-length arguments

   In Ruby, *args is used inside method parentheses to accept any number of arguments.

2. Step 2: Check each option

   def example(*args) is the correct syntax. def example(args*) places the asterisk incorrectly. def example(args) accepts only one argument. def example(&args) uses & which is for blocks.

3. Final Answer:

   def example(*args) -> Option C

4. Quick Check:

   Method with *args = correct syntax [OK]

Hint: Look for asterisk before argument name inside parentheses [OK]

Common Mistakes:

• Placing * after the argument name
• Using & instead of * for arguments
• Omitting the asterisk entirely

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

def greet(*names)
  names.join(", ")
end

puts greet("Alice", "Bob", "Carol")

medium

A. Alice, Bob, Carol

B. ["Alice", "Bob", "Carol"]

C. Alice Bob Carol

D. Error: wrong number of arguments

Solution

1. Step 1: Understand how *names works

   The method collects all arguments into an array called names. Here, it will be ["Alice", "Bob", "Carol"].

2. Step 2: Analyze the join method

   names.join(", ") joins array elements into a string separated by ", ". So the output is "Alice, Bob, Carol".

3. Final Answer:

   Alice, Bob, Carol -> Option A

4. Quick Check:

   Array joined with commas = Alice, Bob, Carol [OK]

Hint: Remember join adds separator between array elements [OK]

Common Mistakes:

• Expecting space-separated output without commas
• Thinking *args returns array string representation
• Assuming error due to multiple arguments

4. Identify the error in this Ruby method definition:

def sum_numbers(*nums)
  total = 0
  nums.each do |n|
    total += n
  end
  total
end

puts sum_numbers(1, 2, '3')

medium

A. Syntax error in method definition

B. Cannot add string '3' to integer total

C. Missing return statement

D. Method does not accept variable arguments

Solution

1. Step 1: Check method logic with variable arguments

   The method sums all numbers in nums using total += n.

2. Step 2: Identify type mismatch error

   Passing '3' as a string causes an error when adding to integer total. Ruby cannot add string and integer directly.

3. Final Answer:

   Cannot add string '3' to integer total -> Option B

4. Quick Check:

   Adding string to integer causes error [OK]

Hint: Check argument types when summing inside *args method [OK]

Common Mistakes:

• Ignoring type mismatch between string and integer
• Assuming method needs explicit return
• Thinking *args causes syntax error

5. You want to write a Ruby method combine that accepts any number of arrays and returns a single array with all elements combined. Which method definition correctly uses *args to achieve this?

hard

A. def combine(*arrays)
arrays.flatten
end

B. def combine(arrays)
arrays.flatten
end

C. def combine(*arrays)
arrays.join
end

D. def combine(*arrays)
arrays.map(&:size)
end

Solution

1. Step 1: Understand the goal

   The method should accept multiple arrays and combine all their elements into one flat array.

2. Step 2: Analyze each option

   def combine(*arrays) arrays.flatten end uses *arrays to accept variable arrays and calls flatten to merge them into one array. def combine(arrays) arrays.flatten end accepts only one argument (an array of arrays). def combine(*arrays) arrays.join end joins arrays into a string, not desired. def combine(*arrays) arrays.map(&:size) end returns sizes, not combined elements.

3. Final Answer:

   def combine(*arrays) arrays.flatten end -> Option A

4. Quick Check:

   Use *args and flatten to combine arrays [OK]

Hint: Use *args plus flatten to merge multiple arrays [OK]

Common Mistakes:

• Not using *args for multiple arrays
• Using join instead of flatten
• Returning sizes instead of combined elements