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

Recall & Review

beginner

What is length validation in Rails?

Length validation checks if the size of a string or array attribute is within a specified range or matches a specific length.

beginner

How do you validate that a username is at least 3 characters long in Rails?

Use validates :username, length: { minimum: 3 } inside the model.

intermediate

What options can you use with length validation in Rails?

You can use minimum, maximum, is (exact length), and within or in (range).

beginner

What happens if a length validation fails when saving a record?

The record is not saved, and errors are added to the model's errors collection for that attribute.

beginner

Show an example of validating a password length between 6 and 12 characters in Rails.

In the model: validates :password, length: { within: 6..12 }

Which option validates that a string is exactly 5 characters long in Rails?

A length: { is: 5 }

B length: { minimum: 5 }

C length: { maximum: 5 }

D length: { within: 3..5 }

The is option checks for exact length.

What does validates :name, length: { minimum: 2 } ensure?

A Name must be between 1 and 2 characters

B Name must be exactly 2 characters

C Name must be at most 2 characters

D Name must be at least 2 characters

The minimum option sets the lowest allowed length.

If a length validation fails, what happens when you try to save the record?

A The record is saved anyway

B An error is raised and the app crashes

C The record is not saved and errors are added to the model

D The record is saved but with a warning

Rails prevents saving and adds errors to the model.

Which length validation option allows specifying a range of valid lengths?

A minimum

B within

C maximum

D is

The within option accepts a range like 3..10.

How do you write a length validation for a field to be between 4 and 8 characters?

A Both B and C

B length: { within: 4..8 }

C length: { minimum: 4, maximum: 8 }

D length: { is: 4..8 }

You can use either within: 4..8 or minimum: 4, maximum: 8.

Explain how to use length validation in a Rails model and what options are available.

Think about how you tell Rails to check string sizes.

Describe what happens behind the scenes when a length validation fails during record saving.

Consider how Rails protects data integrity.