Custom validation rules in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom validation rule in Laravel?

A custom validation rule in Laravel is a user-defined rule that lets you check data in ways not covered by Laravel's built-in validators. It helps you create specific checks for your app's needs.

beginner

How do you create a custom validation rule class in Laravel?

Use the Artisan command: <code>php artisan make:rule RuleName</code>. This creates a class where you define the <code>passes()</code> method to check the value and <code>message()</code> to return an error message.

beginner

What does the passes() method do in a Laravel custom rule?

The passes() method checks if the given value meets your custom condition. It returns true if valid, or false if invalid.

intermediate

How do you apply a custom validation rule to a form request in Laravel?

In your form request's <code>rules()</code> method, add the custom rule class instance to the field's rules array, like <code>'field' => ['required', new RuleName()]</code>.

intermediate

Can custom validation rules accept parameters? How?

Yes. You can pass parameters via the rule class constructor when creating the rule instance. Then use those parameters inside <code>passes()</code> to customize validation.

Which Artisan command creates a custom validation rule class?

A php artisan make:rule RuleName

B php artisan make:validation RuleName

C php artisan create:rule RuleName

D php artisan generate:rule RuleName

The correct command is php artisan make:rule RuleName to create a custom validation rule class.

What should the passes() method return if the value is valid?

A null

B true

C false

D an error message

The passes() method returns true if the value passes validation.

Where do you add a custom validation rule in Laravel?

A In the routes file

B In the controller's constructor

C In the form request's <code>rules()</code> method

D In the model's <code>boot()</code> method

Custom validation rules are added inside the form request's rules() method.

How do you pass parameters to a custom validation rule?

A Via the rule class constructor

B By setting global variables

C Using environment variables

D By modifying the <code>message()</code> method

Parameters are passed to custom rules through the constructor when creating the rule instance.

What does the message() method in a custom rule do?

A Checks if the value is valid

B Defines the validation logic

C Saves the validation result

D Returns the error message when validation fails

The message() method returns the error message shown if validation fails.

Explain how to create and use a custom validation rule in Laravel.

Think about the steps from creating the rule to applying it in validation.

Describe how you can customize a Laravel validation rule with parameters.

Focus on how data flows into the rule class.

Practice

1. What is the main purpose of creating a custom validation rule in Laravel?

easy

A. To define your own logic for validating data beyond built-in rules

B. To change the database schema automatically

C. To create new database tables

D. To generate HTML forms automatically

Solution

1. Step 1: Understand Laravel validation rules

   Laravel provides built-in rules but sometimes you need to check data in a way not covered by them.

2. Step 2: Purpose of custom validation rules

   Custom rules let you write your own logic to validate data exactly as you want.

3. Final Answer:

   To define your own logic for validating data beyond built-in rules -> Option A

4. Quick Check:

   Custom validation = custom logic [OK]

Hint: Custom rules check data your way, not Laravel's default [OK]

Common Mistakes:

• Thinking custom rules change database structure
• Confusing validation with form generation
• Assuming custom rules create tables

2. Which method must you implement in a Laravel custom validation rule class to check if the data passes validation?

easy

A. check

B. message

C. validate

D. passes

Solution

1. Step 1: Recall custom rule methods

   Laravel custom validation rules require two methods: passes and message.

2. Step 2: Identify method for validation logic

   The passes method contains the logic to decide if the data is valid or not.

3. Final Answer:

   passes -> Option D

4. Quick Check:

   passes() checks data validity [OK]

Hint: passes() returns true/false for validation [OK]

Common Mistakes:

• Using message() to check data validity
• Assuming validate() or check() are required methods
• Confusing method names

3. Given this custom rule class snippet, what will $rule->passes('age', 17) return?

class AdultRule implements \Illuminate\Contracts\Validation\Rule {
    public function passes($attribute, $value) {
        return $value >= 18;
    }
    public function message() {
        return 'You must be an adult.';
    }
}

medium

A. true

B. Throws an error

C. false

D. null

Solution

1. Step 1: Understand the passes method logic

   The method returns true if the value is 18 or more, false otherwise.

2. Step 2: Evaluate passes with value 17

   Since 17 is less than 18, the method returns false.

3. Final Answer:

   false -> Option C

4. Quick Check:

   17 < 18 means passes() = false [OK]

Hint: Check condition in passes() with given value [OK]

Common Mistakes:

• Assuming 17 passes as adult
• Thinking passes() throws error for numbers
• Confusing message() with passes()

4. What is wrong with this custom validation rule class?

class EvenNumberRule implements \Illuminate\Contracts\Validation\Rule {
    public function passes($attribute, $value) {
        return $value % 2 == 0
    }
    public function message() {
        return 'The number must be even.';
    }
}

medium

A. message method should return a boolean

B. Missing semicolon after return statement in passes method

C. passes method should accept only one parameter

D. Class must extend a base validation class

Solution

1. Step 1: Check syntax in passes method

   The return statement lacks a semicolon at the end, causing a syntax error.

2. Step 2: Verify other method signatures

   message() correctly returns a string, passes() correctly has two parameters, and implementing the interface is enough.

3. Final Answer:

   Missing semicolon after return statement in passes method -> Option B

4. Quick Check:

   Missing semicolon = syntax error [OK]

Hint: Look for missing semicolons in PHP code [OK]

Common Mistakes:

• Thinking message() must return boolean
• Assuming passes() takes one parameter
• Believing class must extend base class

5. You want to create a custom validation rule that checks if a string contains only vowels. Which approach correctly implements the passes method?

hard

A. return preg_match('/^[aeiouAEIOU]+$/', $value) === 1;

B. return strlen($value) > 0 && ctype_alpha($value);

C. return strpos($value, 'aeiou') !== false;

D. return $value == strtolower($value);

Solution

1. Step 1: Understand the requirement

   The string must contain only vowels (a, e, i, o, u) in any case.

2. Step 2: Analyze each option

   return preg_match('/^[aeiouAEIOU]+$/', $value) === 1; uses regex to check if the string contains only vowels from start to end. return strlen($value) > 0 && ctype_alpha($value); checks only letters but not vowels. return strpos($value, 'aeiou') !== false; checks if 'aeiou' substring exists, which is incorrect. return $value == strtolower($value); checks if string is lowercase, unrelated to vowels.

3. Final Answer:

   return preg_match('/^[aeiouAEIOU]+$/', $value) === 1; -> Option A

4. Quick Check:

   Regex matching only vowels = correct passes() [OK]

Hint: Use regex to match only vowels in string [OK]

Common Mistakes:

• Using ctype_alpha without vowel check
• Checking substring instead of full string
• Confusing case check with vowel check