Any?, all?, none? predicates in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of any? with a block

What is the output of this Ruby code?

Ruby

numbers = [1, 3, 5, 7]
result = numbers.any? { |n| n.even? }
puts result

A RuntimeError

B false

C nil

D true

💡 Hint

Think about whether any number in the array is even.

The any? method returns true if at least one element satisfies the block condition. Here, none are even, so it returns false.

❓ Predict Output

intermediate

Result of all? without a block

What does this Ruby code print?

Ruby

values = [true, 1, 'hello']
puts values.all?

A nil

B false

C true

D ArgumentError

💡 Hint

Without a block, all? checks truthiness of each element.

The all? method without a block returns true if all elements are truthy. Here, all elements are truthy, so it prints true.

❓ Predict Output

advanced

none? with a block returning false

What is the output of this Ruby code?

Ruby

words = ['apple', 'banana', 'cherry']
result = words.none? { |w| w.length > 5 }
puts result

A true

B nil

C TypeError

D false

💡 Hint

Check if any word has length greater than 5.

The none? method returns true if no elements satisfy the block. Here, 'banana' and 'cherry' have length > 5, so none? returns false.

🧠 Conceptual

advanced

Understanding all? with mixed truthy and falsy values

Given the array [nil, true, false], what does all? return when called without a block?

A false

B true

C nil

D ArgumentError

💡 Hint

Remember that all? checks truthiness of each element.

Since nil and false are falsy in Ruby, all? returns false when called without a block.

❓ Predict Output

expert

Complex predicate with any?, all?, none?

What is the output of this Ruby code?

Ruby

data = [0, nil, false, '']
result = [
  data.any?,
  data.all?,
  data.none?
]
puts result.inspect

A [true, false, false]

B [false, false, true]

C [true, true, false]

D [false, true, false]

💡 Hint

Recall that only false and nil are falsy; zero and empty string are truthy.

any? returns true because 0 and '' are truthy.
all? returns false because nil and false are falsy.
none? returns false because there are truthy elements (0 and '').