Numericality validation in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of numericality validation in Rails?

Numericality validation ensures that a model attribute contains only numbers, helping to keep data accurate and consistent.

beginner

How do you add a basic numericality validation to a Rails model attribute?

Use validates :attribute_name, numericality: true inside the model to check that the attribute is a number.

intermediate

What option would you use to allow only integers in numericality validation?

Add only_integer: true like validates :age, numericality: { only_integer: true } to accept only whole numbers.

intermediate

How can you validate that a number is greater than or equal to 0 using numericality validation?

Use the greater_than_or_equal_to: 0 option, for example: validates :price, numericality: { greater_than_or_equal_to: 0 }.

beginner

What happens if a non-numeric value is assigned to an attribute with numericality validation?

The model will be invalid and saving it will fail. Rails adds an error message to the attribute explaining it must be a number.

Which validation ensures an attribute is a number in Rails?

A presence

B numericality

C uniqueness

D length

The numericality validation checks that the attribute contains a valid number.

How do you restrict a numericality validation to only allow integers?

A is_integer: true

B integer_only: true

C integer: true

D only_integer: true

The correct option is only_integer: true to allow only whole numbers.

What option would you use to ensure a number is greater than 10?

A greater_than: 10

B min: 10

C above: 10

D greater_or_equal: 10

Use greater_than: 10 to require the number to be strictly more than 10.

If you want to allow nil values but validate numbers when present, what option do you add?

A skip_nil: true

B optional: true

C allow_nil: true

D ignore_nil: true

allow_nil: true lets the attribute be empty but validates if a number is given.

What error message appears if a non-numeric value is assigned to a numericality validated attribute?

A "is not a number"

B "can't be blank"

C "is invalid"

D "must be unique"

Rails adds the error message "is not a number" for numericality validation failures.

Explain how to use numericality validation in a Rails model to accept only positive integers.

Think about combining options inside numericality.

Describe what happens when you try to save a Rails model with a non-numeric value on a numericality validated attribute.

Consider validation failure behavior.