Parameters with default values in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method with default parameters

What is the output of this Ruby code?

Ruby

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

puts greet("Alice")

A Hello, Guest!

B Alice, Hello!

C Hello, Alice!

D Error: wrong number of arguments

💡 Hint

Check which parameters are given and which use default values.

The method greet has two parameters with default values. When called with one argument, the first parameter is set to "Alice" and the second uses its default "Hello". So the output is "Hello, Alice!".

❓ Predict Output

intermediate

Method call with all default parameters

What will this Ruby code print?

Ruby

def calculate(a = 5, b = 10)
  a * b
end

puts calculate

A 50

B 15

C Error: wrong number of arguments

D 0

💡 Hint

No arguments are passed, so all default values are used.

Both parameters a and b use their default values 5 and 10. The method returns 5 * 10 = 50.

🔧 Debug

advanced

Identify the error in method with default parameters

What error does this Ruby code raise when run?

Ruby

def add(x, y = 2, z)
  x + y + z
end

puts add(1, 3, 4)

A No error, outputs 8

B SyntaxError: default argument followed by non-default argument

C TypeError: undefined method '+' for nil:NilClass

D ArgumentError: wrong number of arguments (given 3, expected 2)

💡 Hint

In Ruby, parameters with default values must come after parameters without defaults.

Ruby does not allow a parameter with a default value (y=2) to be followed by a parameter without a default (z). This causes a SyntaxError.

❓ Predict Output

advanced

Output with mixed default and explicit parameters

What is the output of this Ruby code?

Ruby

def info(name = "Unknown", age = 0, city = "Nowhere")
  "#{name} is #{age} years old and lives in #{city}."
end

puts info("Bob", city: "Paris")

A Bob is city: Paris years old and lives in Nowhere.

B Bob is 0 years old and lives in Nowhere.

C Bob is 0 years old and lives in Paris.

D Error: wrong number of arguments

💡 Hint

Check how Ruby handles keyword arguments versus positional arguments.

The method expects positional arguments, but city: "Paris" is a keyword argument. Ruby raises an ArgumentError because the method does not accept keyword arguments.

🧠 Conceptual

expert

Number of parameters in method with defaults and splat

Given this Ruby method, how many arguments can it accept without error?

Ruby

def example(a, b = 2, *c, d)
  [a, b, c, d]
end

A At least 2 arguments, no maximum limit

B Exactly 4 arguments only

C At least 3 arguments, no maximum limit

D At least 1 argument, no maximum limit

💡 Hint

Consider required, optional, splat, and default parameters in Ruby.

'a' is required. 'b' has a default value, making it optional. '*c' collects any number (including zero) of additional arguments. 'd' is a required positional parameter after the splat. Therefore, at least 2 arguments are required (one for 'a' and one for 'd'), with no maximum due to the splat '*c'.