# Controllers

`Controller` 是将应用程序的不同逻辑进行分组的优秀方案，大多数 Controller 都具备接受多种请求的功能，并根据需要进行响应。

建议将其放在 [Controllers](../getting-started/folder-structure.md#controllers) 文件夹下，具体情况可以根据需求划分模块。


## 概述

让我们看一个示例 Controller：

```swift
import Vapor

struct TodosController: RouteCollection {
    func boot(routes: RoutesBuilder) throws {
        let todos = routes.grouped("todos")
        todos.get(use: index)
        todos.post(use: create)

        todos.group(":id") { todo in
            todo.get(use: show)
            todo.put(use: update)
            todo.delete(use: delete)
        }
    }

    func index(req: Request) async throws -> [Todo] {
        try await Todo.query(on: req.db).all()
    }

    func create(req: Request) async throws -> Todo {
        let todo = try req.content.decode(Todo.self)
        try await todo.save(on: req.db)
        return todo
    }

    func show(req: Request) async throws -> Todo {
        guard let todo = try await Todo.find(req.parameters.get("id"), on: req.db) else {
            throw Abort(.notFound)
        }
        return todo
    }

    func update(req: Request) async throws -> Todo {
        guard let todo = try await Todo.find(req.parameters.get("id"), on: req.db) else {
            throw Abort(.notFound)
        }
        let updatedTodo = try req.content.decode(Todo.self)
        todo.title = updatedTodo.title
        try await todo.save(on: req.db)
        return todo
    }

    func delete(req: Request) async throws -> HTTPStatus {
        guard let todo = try await Todo.find(req.parameters.get("id"), on: req.db) else {
            throw Abort(.notFound)
        }
        try await todo.delete(on: req.db)
        return .ok
    }
}
```

`Controller` 的方法接受 `Request` 参数，并返回 `ResponseEncodable` 对象。该方法可以是异步或者同步。    

最后，你需要在 `routes.swift` 中注册 Controller：

```swift
try app.register(collection: TodosController())
```