Single action controllers in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this single action controller?

Consider this Laravel single action controller. What will be the HTTP response content when this controller is called?

Laravel

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class WelcomeController
{
    public function __invoke(Request $request)
    {
        return response('Hello, Laravel!');
    }
}

A A 404 Not Found error response

B A redirect response to the home page '/'

C A plain text HTTP response with content 'Hello, Laravel!'

D A JSON response with content {"message": "Hello, Laravel!"}

💡 Hint

Single action controllers use the __invoke method to handle requests.

The __invoke method returns a plain text response with the string 'Hello, Laravel!'. This is the content the client receives.

📝 Syntax

intermediate

Which option correctly defines a single action controller in Laravel?

Select the code snippet that correctly defines a single action controller class in Laravel.

A class UserController { public function __invoke() { return 'User'; } }

B class UserController { public function handle() { return 'User'; } }

C class UserController { public function index() { return 'User'; } }

D class UserController { public function __call() { return 'User'; } }

💡 Hint

Single action controllers use the magic __invoke method.

Only the __invoke method allows the controller to be called as a single action.

❓ state_output

advanced

What is the output after calling this single action controller with a request?

Given this controller, what will be the output when accessed via a web route?

Laravel

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class CounterController
{
    private int $count = 0;

    public function __invoke(Request $request)
    {
        $this->count++;
        return "Count is: {$this->count}";
    }
}

A Count is: 1

B Count is: 2

C Count is: 0

D Error: Cannot access private property

💡 Hint

Each request creates a new controller instance.

The count starts at 0 and increments once per request. Since each request is new, count is always 1.

🔧 Debug

advanced

Why does this single action controller cause a routing error?

This controller is registered in routes/web.php as Route::get('/test', TestController::class); but accessing '/test' gives a 500 error. What is the problem?

Laravel

<?php

namespace App\Http\Controllers;

class TestController
{
    public function handle()
    {
        return 'Test';
    }
}

A The controller namespace is incorrect.

B The handle method is private and cannot be accessed.

C The route should use a closure, not a controller class.

D The controller lacks an __invoke method required for single action controllers.

💡 Hint

Single action controllers must have __invoke method.

When routing to a controller class without specifying a method, Laravel calls __invoke. Missing it causes error.

🧠 Conceptual

expert

What is a key advantage of using single action controllers in Laravel?

Choose the best explanation for why developers use single action controllers.

A They enable automatic database migrations when routes are registered.

B They simplify controllers by focusing on one action, improving readability and testability.

C They automatically cache responses without extra code.

D They allow multiple HTTP methods to be handled in one controller method.

💡 Hint

Think about controller responsibilities and code clarity.

Single action controllers have one job, making code easier to read, maintain, and test.

Practice

1. What is the main purpose of a single action controller in Laravel?

easy

A. To replace middleware functionality

B. To manage multiple actions in one controller

C. To handle exactly one action using the __invoke method

D. To handle database migrations

Solution

1. Step 1: Understand the role of single action controllers

   Single action controllers are designed to handle only one action, making code simpler and focused.

2. Step 2: Identify the method used

   They use the special __invoke method to handle that single action.

3. Final Answer:

   To handle exactly one action using the __invoke method -> Option C

4. Quick Check:

   Single action controller = __invoke method [OK]

Hint: Single action controllers always use __invoke method [OK]

Common Mistakes:

• Thinking they handle multiple actions
• Confusing with middleware or migrations
• Assuming they require multiple methods

2. Which of the following is the correct syntax to define a single action controller in Laravel?

easy

A. class MyController { public function __invoke() {} }

B. class MyController { public function handle() {} }

C. class MyController { public function index() {} }

D. class MyController { public function action() {} }

Solution

1. Step 1: Recall the special method for single action controllers

   Single action controllers use the __invoke() method to handle the action.

2. Step 2: Match the syntax

   The correct syntax defines a class with a public function __invoke() method.

3. Final Answer:

   class MyController { public function __invoke() {} } -> Option A

4. Quick Check:

   __invoke method syntax = class MyController { public function __invoke() {} } [OK]

Hint: Look for __invoke method in the class [OK]

Common Mistakes:

• Using index() or handle() instead of __invoke()
• Forgetting the public visibility
• Confusing method names with other controller types

3. Given this single action controller code, what will be the output when accessed?

class WelcomeController {
    public function __invoke() {
        return 'Hello, Laravel!';
    }
}

medium

A. Hello, Laravel!

B. Error: Method not found

C. Empty response

D. 404 Not Found

Solution

1. Step 1: Understand __invoke method behavior

   The __invoke method runs when the controller is called as a single action, returning the string 'Hello, Laravel!'.

2. Step 2: Predict the output

   Since the method returns a string, the response will be that string displayed.

3. Final Answer:

   Hello, Laravel! -> Option A

4. Quick Check:

   __invoke returns string = 'Hello, Laravel!' [OK]

Hint: __invoke returns output directly as response [OK]

Common Mistakes:

• Expecting an error due to missing method name
• Thinking it returns empty or 404
• Confusing with multi-method controllers

4. Identify the error in this single action controller code:

class TestController {
    public function invoke() {
        return 'Test';
    }
}

medium

A. Return statement is invalid

B. Method should be private, not public

C. Class name must be TestActionController

D. Missing __invoke method name with double underscores

Solution

1. Step 1: Check method name for single action controller

   The method must be named __invoke with two underscores, not invoke.

2. Step 2: Verify method visibility and return

   Method should be public and return a value, which is correct here.

3. Final Answer:

   Missing __invoke method name with double underscores -> Option D

4. Quick Check:

   Method name must be __invoke [OK]

Hint: Method must be named __invoke with double underscores [OK]

Common Mistakes:

• Using invoke instead of __invoke
• Changing method visibility incorrectly
• Assuming class name affects single action controller

5. You want to create a single action controller that returns a JSON response with a message 'Success'. Which code snippet correctly implements this?

hard

A. class JsonResponseController {
public function __invoke() {
return json_encode(['message' => 'Success']);
}
}

B. class JsonResponseController {
public function __invoke() {
return response()->json(['message' => 'Success']);
}
}

C. class JsonResponseController {
private function __invoke() {
return ['message' => 'Success'];
}
}

D. class JsonResponseController {
public function handle() {
return json(['message' => 'Success']);
}
}

Solution

1. Step 1: Use __invoke method for single action controller

   The controller must have a public __invoke() method to be a single action controller.

2. Step 2: Return a proper JSON response in Laravel

   Use Laravel's response()->json() helper to return a JSON response correctly.

3. Final Answer:

   class JsonResponseController { public function __invoke() { return response()->json(['message' => 'Success']); } } -> Option B

4. Quick Check:

   __invoke + response()->json() = class JsonResponseController { public function __invoke() { return response()->json(['message' => 'Success']); } } [OK]

Hint: Use response()->json() inside __invoke method [OK]

Common Mistakes:

• Using handle() instead of __invoke()
• Returning raw arrays without response helper
• Using json() function which doesn't exist in Laravel