In web development, actions in the controller are used to process user requests and return responses. Controller is the classification of requests, while action is specific operations. For example, UserController contains index, show, create and other actions, each corresponding to a specific URL routing and HTTP method. Ruby on Rails defines actions through def, and parameters are obtained through params; Laravel allows parameters to be directly used as method parameters; ASP.NET MVC uses C#, with clear structure but strict syntax. Action usually includes three steps: receiving parameters, calling model processing logic, and returning response. Pay attention to the parameter delivery method, single responsibilities, exception handling and unified API response format. Common problems include name conflicts, routing configuration errors, testing difficulties, and code reuse, which can be solved by standardized naming, correct routing binding, alternative service design, and extraction of public methods.

In web development, defining actions in controllers is the core step in implementing user request responses. Simply put, an action is a method that handles a specific HTTP request and returns the corresponding result. Different frameworks have different writing styles, but the basic ideas are the same.

1. Understand the relationship between controller and action

Controller can be understood as "requested classification", and action is the specific operation under this classification. For example:

• UserController may contain index , show , create , update , delete and other actions.
• Each action corresponds to a URL route, such as /users corresponds to index , and /users/1 corresponds to show .

Generally, the naming of an action is associated with an HTTP method:

• GET /users → index
• GET /users/1 → show
• POST /users → create
• PUT /users/1 → update
• DELETE /users/1 → delete

2. How to define action in common frameworks

Ruby on Rails

 class UsersController < ApplicationController
  def index
    @users = User.all
    render json: @users
  end

  def show
    @user = User.find(params[:id])
    render json: @user
  end
end

Here each def ... end is an action. Note that params[:id] is the way to get parameters from the URL.

Laravel (PHP)

 class UserController extends Controller
{
    public function index()
    {
        $users = User::all();
        return response()->json($users);
    }

    public function show($id)
    {
        $user = User::find($id);
        return response()->json($user);
    }
}

In Laravel, parameters can be passed directly as method parameters, which is more intuitive.

ASP.NET MVC (C#)

 public class UserController : Controller
{
    public IActionResult Index()
    {
        var users = db.Users.ToList();
        return Json(users);
    }

    public IActionResult Show(int id)
    {
        var user = db.Users.Find(id);
        return Json(user);
    }
}

C# has a more stringent syntax, but is well-structured and suitable for large projects.

3. Common Structures and Precautions for Action

A typical action generally includes the following steps:

• Receive request parameters (such as id, form data, etc.)
• Calling the model or service layer to process business logic
• Return response (JSON, HTML page, redirect, etc.)

Details to note:

• Parameter delivery methods vary from framework to framework, some pass through params arrays, and some pass through method parameters.
• Don't do too much in one action and keep your responsibilities single.
• Exception handling is very important, especially database query failures.
• If it is an API, unified return formats (such as with status code and message fields) will be better maintained.

4. FAQs and Suggestions

• Action Name Conflict : Some frameworks have requirements for action names, such as they must be public and cannot be repeated with the parent class method.
• Routing configuration mismatch : Even if the action is written, it cannot be accessed if it is not bound to the route correctly.
• Testing difficulty : Try to make the service called by action be replaced, which is convenient for unit testing.
• Code reuse : Multiple public parts of the action can be drawn into private methods.

Basically that's it. Different languages and frameworks have slightly different writing methods, but as long as you understand the role of controller and action, you can get started quickly.

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