Numericality validation in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to validate that the age attribute is a number.

Ruby on Rails

validates :age, [1]: true

Drag options to blanks, or click blank then click option'

Auniqueness

Bpresence

Cnumericality

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using presence instead of numericality

Using uniqueness which checks for duplicates

Using length which checks string length

The numericality validator ensures the attribute is a number.

2fill in blank

medium

Complete the code to validate that the price attribute is a number greater than 0.

Ruby on Rails

validates :price, numericality: { [1]: 0 }

Drag options to blanks, or click blank then click option'

Agreater_than

Bless_than

Cequal_to

Donly_integer

Attempts:

3 left

💡 Hint

Common Mistakes

Using less_than instead of greater_than

Using equal_to which checks for exact value

Using only_integer which restricts to integers only

The option greater_than: 0 ensures the number is more than zero.

3fill in blank

hard

Fix the error in the validation to allow only integer values for quantity.

Ruby on Rails

validates :quantity, numericality: { [1]: true }

Drag options to blanks, or click blank then click option'

Aonly_integer

Bonly_float

Cgreater_than_or_equal_to

Dless_than_or_equal_to

Attempts:

3 left

💡 Hint

Common Mistakes

Using only_float which allows decimals

Using greater_than_or_equal_to which sets a range

Using less_than_or_equal_to which sets a range

The only_integer: true option restricts the value to integers only.

4fill in blank

hard

Fill both blanks to validate that score is an integer between 1 and 10 inclusive.

Ruby on Rails

validates :score, numericality: { only_integer: true, [1]: 1, [2]: 10 }

Drag options to blanks, or click blank then click option'

Agreater_than_or_equal_to

Bless_than

Cless_than_or_equal_to

Dgreater_than

Attempts:

3 left

💡 Hint

Common Mistakes

Using less_than instead of less_than_or_equal_to

Using greater_than instead of greater_than_or_equal_to

Mixing up the order of options

Use greater_than_or_equal_to and less_than_or_equal_to to set inclusive range limits.

5fill in blank

hard

Fill all three blanks to validate that discount is a number, greater than or equal to 0, and less than 1.

Ruby on Rails

validates :discount, numericality: { [1]: true, [2]: 0, [3]: 1 }

Drag options to blanks, or click blank then click option'

Aonly_integer

Bgreater_than_or_equal_to

Cless_than

Dgreater_than

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater_than instead of greater_than_or_equal_to

Using less_than_or_equal_to instead of less_than

Omitting only_integer when integers are required

The validation requires only_integer: true to restrict to integers, and range limits with greater_than_or_equal_to: 0 and less_than: 1.

Practice

1. What does the validates :age, numericality: true line do in a Rails model?

easy

A. It checks if age is a string.

B. It makes the age attribute required.

C. It ensures the age attribute is a number.

D. It sets a default value for age.

Solution

1. Step 1: Understand numericality validation

   The numericality: true option checks if the attribute is a number.

2. Step 2: Apply to age attribute

   Since it is applied to age, it ensures age must be numeric.

3. Final Answer:

   It ensures the age attribute is a number. -> Option C

4. Quick Check:

   Numericality validation = ensures number [OK]

Hint: Numericality means the value must be a number [OK]

Common Mistakes:

• Confusing numericality with presence validation
• Thinking it sets default values
• Assuming it checks for strings

2. Which of the following is the correct syntax to validate that price is an integer in Rails?

easy

A. validates :price, numericality: { only_integer: true }

B. validates :price, integer: true

C. validates :price, number: { integer: true }

D. validates :price, numericality: true, integer: true

Solution

1. Step 1: Recall correct numericality syntax

   Rails uses numericality: { only_integer: true } to check integers.

2. Step 2: Check options

   validates :price, numericality: { only_integer: true } matches this syntax exactly; others are invalid or incorrect.

3. Final Answer:

   validates :price, numericality: { only_integer: true } -> Option A

4. Quick Check:

   Integer validation uses only_integer: true [OK]

Hint: Use only_integer inside numericality hash [OK]

Common Mistakes:

• Using a separate integer key instead of inside numericality
• Writing invalid keys like number or integer alone
• Missing curly braces for options

3. Given this model validation:

validates :score, numericality: { greater_than: 0, less_than_or_equal_to: 100 }

What happens if you try to save score = 150?

medium

A. Validation fails because 150 is greater than 100.

B. The record saves successfully.

C. Validation fails because 150 is less than 0.

D. Validation passes because 150 is a number.

Solution

1. Step 1: Understand validation limits

   The validation requires score to be greater than 0 and less than or equal to 100.

2. Step 2: Check the value 150

   150 is greater than 100, so it violates the less_than_or_equal_to: 100 rule.

3. Final Answer:

   Validation fails because 150 is greater than 100. -> Option A

4. Quick Check:

   Value must be ≤ 100, 150 fails [OK]

Hint: Check all numerical limits carefully [OK]

Common Mistakes:

• Ignoring upper limit and assuming number is valid
• Confusing greater_than with greater_than_or_equal_to
• Assuming any number passes

4. Identify the error in this validation:

validates :quantity, numericality: { only_integer: true, greater_than: 0, less_than: 10, message: 'must be a number' }

medium

A. There is no error; this validation is correct.

B. The message option is misplaced inside the numericality hash.

C. The validation is missing presence: true.

D. The only_integer option cannot be combined with greater_than.

Solution

1. Step 1: Check placement of message

   The message option should be outside the numericality options hash, not inside it.

2. Step 2: Validate other options

   only_integer, greater_than, and less_than can be combined correctly.

3. Final Answer:

   The message option is misplaced inside the numericality hash. -> Option B

4. Quick Check:

   Message option goes outside numericality hash [OK]

Hint: Put message outside numericality options hash [OK]

Common Mistakes:

• Placing message inside numericality hash
• Thinking only_integer conflicts with other options
• Assuming presence is required for numericality

5. You want to validate a rating attribute that must be an integer between 1 and 5 inclusive. Which validation code correctly enforces this?

hard

A. validates :rating, numericality: { only_integer: true, greater_than: 1, less_than: 5 }

B. validates :rating, numericality: { only_integer: true, greater_than: 1, less_than_or_equal_to: 5 }

C. validates :rating, numericality: { only_integer: true, greater_than_or_equal_to: 1, less_than: 5 }

D. validates :rating, numericality: { only_integer: true, greater_than_or_equal_to: 1, less_than_or_equal_to: 5 }

Solution

1. Step 1: Understand inclusive range requirements

   The rating must include 1 and 5, so use greater_than_or_equal_to: 1 and less_than_or_equal_to: 5.

2. Step 2: Check integer enforcement

   only_integer: true ensures rating is an integer.

3. Step 3: Compare options

   validates :rating, numericality: { only_integer: true, greater_than_or_equal_to: 1, less_than_or_equal_to: 5 } matches all requirements exactly; others exclude 1 or 5 or use wrong operators.

4. Final Answer:

   validates :rating, numericality: { only_integer: true, greater_than_or_equal_to: 1, less_than_or_equal_to: 5 } -> Option D

5. Quick Check:

   Inclusive integer range uses >= and <= [OK]

Hint: Use greater_than_or_equal_to and less_than_or_equal_to for inclusive range [OK]

Common Mistakes:

• Using greater_than or less_than excludes boundary values
• Forgetting only_integer for integer check
• Mixing up operators for inclusive range