Parameters with default values in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method with a default parameter value.

Ruby

def greet(name = [1])
  puts "Hello, #{name}!"
end

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

A"name"

BGuest

Cname

D"Guest"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the default string value.

Using a variable name instead of a string literal.

The default value for the parameter name should be a string, so it must be enclosed in quotes.

2fill in blank

medium

Complete the code to call the method with and without the default parameter.

Ruby

def greet(name = "Guest")
  puts "Hello, #{name}!"
end

greet([1])
greet

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

AAlice

B"Alice"

Cname

D"name"

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the method with a name without quotes.

Confusing the method call syntax.

When calling the method with a specific name, it must be a string with quotes.

3fill in blank

hard

Fix the error in the method definition with a default parameter.

Ruby

def add_numbers(a, b = [1])
  a + b
end

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

Anil

B"0"

C0

Da

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "0" instead of number 0 as default.

Using a variable name as default value.

The default value for b should be a number, so 0 is correct.

4fill in blank

hard

Fill both blanks to create a method with two parameters, one with a default value.

Ruby

def order(item, quantity = [1])
  puts "Order: #{quantity} #{item}(s)"
end

order("apple", [2])

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

A1

B"apple"

C5

Dquantity

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for quantity.

Confusing parameter names with values.

The default quantity is 1, and the method call uses 5 as the quantity.

5fill in blank

hard

Fill all three blanks to define a method with default parameters and call it correctly.

Ruby

def book_flight(destination = [1], seats = [2])
  puts "Booking #{seats} seats to #{destination}."
end

book_flight([3])

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

A"Paris"

B2

C"Tokyo"

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of parameters.

Using numbers as strings or vice versa.

The method defaults to "Paris" and 2 seats, but the call overrides the destination to "Tokyo".

Practice

1. What does a default parameter value in a Ruby method do?
def greet(name = "Guest")

easy

A. It causes a syntax error if the argument is missing.

B. It makes the parameter mandatory every time the method is called.

C. It changes the method name automatically.

D. It allows the method to be called without that argument, using the default instead.

Solution

1. Step 1: Understand default parameter purpose

   Default parameters provide a fallback value if no argument is given.

2. Step 2: Apply to the example method

   In def greet(name = "Guest"), if no name is passed, "Guest" is used.

3. Final Answer:

   It allows the method to be called without that argument, using the default instead. -> Option D

4. Quick Check:

   Default parameter = fallback value [OK]

Hint: Default means optional argument with fallback value [OK]

Common Mistakes:

• Thinking default parameters are mandatory
• Assuming missing arguments cause errors
• Confusing default values with method overloading

2. Which of the following is the correct syntax to define a method with a default parameter in Ruby?

easy

A. def add(a, b = 5); a + b; end

B. def add(a =, b 5); a + b; end

C. def add(a, b: 5); a + b; end

D. def add(a, b); b = 5; a + b; end

Solution

1. Step 1: Review Ruby default parameter syntax

   Default values are set with = value after the parameter name.

2. Step 2: Check each option

   def add(a, b = 5); a + b; end uses b = 5 correctly. def add(a =, b 5); a + b; end has invalid syntax. def add(a, b: 5); a + b; end uses keyword argument style, not default parameter. def add(a, b); b = 5; a + b; end assigns inside method body, not default parameter.

3. Final Answer:

   def add(a, b = 5); a + b; end -> Option A

4. Quick Check:

   Default param syntax = param = value [OK]

Hint: Use = after parameter name for default values [OK]

Common Mistakes:

• Using colon instead of equals for default values
• Placing = before parameter name
• Assigning default inside method body instead of parameter list

3. What is the output of this Ruby code?

def multiply(x, y = 2)
  x * y
end

puts multiply(4)
puts multiply(4, 3)

medium

A. 8\n12

B. 4\n7

C. Error: missing argument

D. 6\n12

Solution

1. Step 1: Analyze method calls with default parameter

   First call: multiply(4) uses default y=2, so 4*2=8. Second call: multiply(4,3) uses y=3, so 4*3=12.

2. Step 2: Determine output of puts statements

   Outputs are printed on separate lines: 8 then 12.

3. Final Answer:

   8 12 -> Option A

4. Quick Check:

   Default param used when missing = 8, explicit param = 12 [OK]

Hint: Default used if argument missing, else given value [OK]

Common Mistakes:

• Expecting error when argument is missing
• Confusing default parameter with keyword arguments
• Mixing up output values

4. Identify the error in this Ruby method definition:

def greet(name = "Guest", age)
  "Hello #{name}, you are #{age} years old."
end

medium

A. Method name cannot be 'greet' with parameters.

B. Missing return statement causes error.

C. Default parameters must come after non-default parameters.

D. String interpolation syntax is incorrect.

Solution

1. Step 1: Check parameter order rules in Ruby

   Parameters with default values must be placed after parameters without defaults.

2. Step 2: Analyze given method signature

   Here, name has default, but age does not and comes after. This causes syntax error.

3. Final Answer:

   Default parameters must come after non-default parameters. -> Option C

4. Quick Check:

   Default params after required params [OK]

Hint: Put default params after required ones [OK]

Common Mistakes:

• Placing default parameters before required ones
• Assuming return statement is mandatory
• Misreading string interpolation syntax

5. You want to define a method order that takes a product name and an optional quantity with default 1. Which is the best way to define it to allow calling order("apple") and order("apple", 5)?

hard

A. def order(product = "apple", quantity); "Order #{quantity} #{product}(s)"; end

B. def order(product, quantity = 1); "Order #{quantity} #{product}(s)"; end

C. def order(quantity = 1, product); "Order #{quantity} #{product}(s)"; end

D. def order(product, quantity); quantity ||= 1; "Order #{quantity} #{product}(s)"; end

Solution

1. Step 1: Identify correct parameter order and defaults

   Required parameters come first, then optional with default values.

2. Step 2: Evaluate each option

   def order(product, quantity = 1); "Order #{quantity} #{product}(s)"; end correctly places product first and quantity with default 1 second. def order(product = "apple", quantity); "Order #{quantity} #{product}(s)"; end has default before required, invalid. def order(quantity = 1, product); "Order #{quantity} #{product}(s)"; end swaps order incorrectly. def order(product, quantity); quantity ||= 1; "Order #{quantity} #{product}(s)"; end assigns default inside method but requires both arguments.

3. Final Answer:

   def order(product, quantity = 1); "Order #{quantity} #{product}(s)"; end -> Option B

4. Quick Check:

   Required first, default second = def order(product, quantity = 1); "Order #{quantity} #{product}(s)"; end [OK]

Hint: Put required params first, defaults after [OK]

Common Mistakes:

• Placing default parameter before required
• Assigning default inside method body instead of parameter list
• Confusing parameter order