Any?, all?, none? predicates in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the any? method do in Ruby?

The any? method checks if at least one element in a collection meets a condition. It returns true if any element matches, otherwise false.

beginner

How does the all? method work in Ruby?

The all? method returns true only if every element in the collection meets the given condition. If any element does not match, it returns false.

beginner

Explain the purpose of the none? method in Ruby.

The none? method returns true if no elements in the collection meet the condition. It returns false if at least one element matches.

beginner

What will [1, 2, 3].any? { |n| n > 2 } return?

It will return true because at least one element (3) is greater than 2.

beginner

What is the result of [1, 2, 3].all? { |n| n < 4 }?

It returns true because all elements (1, 2, 3) are less than 4.

What does none? return when no elements satisfy the condition?

A nil

B false

C true

D raises an error

none? returns true if no elements meet the condition.

Which method returns true if at least one element matches the condition?

A any?

B none?

C select

D all?

any? returns true if any element matches.

What will [4, 5, 6].all? { |n| n > 3 } return?

A false

B true

C nil

D raises an error

All elements are greater than 3, so all? returns true.

If any? returns false, what can you say about the elements?

A No elements match the condition

B All elements match the condition

C Some elements match the condition

D The collection is empty

any? returns false only if no elements match.

Which method would you use to check if every element is even?

A find { |n| n.even? }

B any? { |n| n.even? }

C none? { |n| n.even? }

D all? { |n| n.even? }

all? checks if all elements satisfy the condition.

Describe how any?, all?, and none? differ in checking conditions on collections.

Think about how many elements need to satisfy the condition for each method.

Give an example of when you would use none? in a Ruby program.

Consider situations where you want to confirm absence of a condition.