swift - 使 Vapor API 响应符合 JSON API 规范

Question

我有一个用 Vapor 编写的 API。我想遵循 JSON API 规范。

我很难理解如何以正确的格式创建我的响应对象。

例如，我希望我的回复结构如下...

{
  "links": {
    "self": "http://example.com/dish",
    "next": "http://example.com/dish?page=2",
    "last": "http://example.com/dish?page=10"
  },
  "data": [{
    "title": "Spag Bol",
    "course": "main",
    "description": "BasGetti",
    "price": 3.9900000000000002
  },
  {
    "title": "Ice Cream",
    "course": "desert",
    "description": "Vanilla",
    "price": 0.98999999999999999
  }]
}

如果 POST 到这个端点(伪代码)，我可以非常简单地返回数据的内容

router.post(Dish.self, at: "api/dish") { req, data -> Future<Dish> in
    return Future.map(on: req, { () -> Dish in
        data.id = 001
        return data
    })
}

我尝试创建一个 ApiResponse 类并传入数据，这样我就可以构建响应，但这并没有解决错误 Cannot convert return expression of type 'ApiResonse' to return type '菜'

   router.post(Dish.self, at: "api/dish") { req, data -> Future<Dish> in
        return Future.map(on: req, { () -> Dish in
            data.id = 001
            return ApiResonse(links: Links(self: "http://google.com", next: "http://google.com", last: "http://google.com"), data: data)
        })
    }

我不确定我该怎么做。这些是尝试过的类(class)

final class Dish: Content {
    var id: Int?
    var title: String
    var description: String
    var course: String
    var price: Double

    init(title: String, description: String, course: String, price: Double) {
        self.title = title
        self.description = description
        self.course = course
        self.price = price
    }
}

struct Links {
    var `self`: String?
    var next: String?
    var last: String?
}

class ApiResonse {
    var links: Links?
    var data: Any

    init(links: Links, data: Any) {
        self.links = links
        self.data = data
    }
}

我是否需要使用泛型来设置响应类？谁能举个例子？

Answer 1

1. 每个 class或 struct在复合对象中 ApiResponse需要遵守 Content协议(protocol)。 Content协议(protocol)包括 Codable JSON解码和编码协议(protocol)。

2. 注意 Any 不符合Codable协议(protocol)，因此 Any 不能用作响应的任何组成部分。参见 Vapor 3 Docs: "Using Content"和 Vapor 4 Docs: "Content"获取更多详细信息。

   Vapor 3: all content types (JSON, protobuf, URLEncodedForm, Multipart, etc) are treated the same. All you need to parse and serialize content is a Codable class or struct.

   Vapor 4: Vapor's content API allows you to easily encode / decode Codable structs to / from HTTP messages.

3. 完全符合 Content 的对象或复合对象可以用作 ResponseEncodable响应。

4. ApiResponse当每个路由端点解析为特定的 Content 时，模型可以是通用的协议(protocol)兼容类型。

带有以下代码的示例项目在 GitHub: VaporExamplesLab/Example-SO-VaporJsonResponse 上.

示例模型

struct Dish: Content {
    var id: Int?
    var title: String
    var description: String
    var course: String
    var price: Double
    
    init(id: Int? = nil, title: String, description: String, course: String, price: Double) {
        self.id = id
        self.title = title
        self.description = description
        self.course = course
        self.price = price
    }
}

struct Links: Content {
    var current: String?
    var next: String?
    var last: String?
}

struct ApiResponse: Content {
    var links: Links?
    var dishes: [Dish]
    
    init(links: Links, dishes: [Dish]) {
        self.links = links
        self.dishes = dishes
    }
}

示例 POST : 返回 ApiResponse

router.post(Dish.self, at: "api/dish") { 
    (request: Request, dish: Dish) -> ApiResponse in
    var dishMutable = dish
    dishMutable.id = 001
    
    var links = Links()
    links.current = "http://example.com"
    links.next = "http://example.com"
    links.last = "http://example.com"

    return ApiResponse(links: links, dishes: [dishMutable])
}

示例 POST : 返回 Future<ApiResponse>

router.post(Dish.self, at: "api/dish-future") { 
    (request: Request, dish: Dish) -> Future<ApiResponse> in
    var dishMutable = dish
    dishMutable.id = 002
    
    var links = Links()
    links.current = "http://example.com"
    links.next = "http://example.com"
    links.last = "http://example.com"
    
    return Future.map(on: request, { 
        () -> ApiResponse in
        return ApiResponse(links: links, dishes: [dishMutable])
    }) 
}

收到 JSON 响应

上述代码的响应主体产生以下内容:

{
  "links": {
    "current": "http://example.com",
    "next": "http://example.com",
    "last": "http://example.com"
  },
  "dishes": [
    {
      "id": 1,
      "title": "Aztec Salad",
      "description": "Flavorful Southwestern ethos with sweet potatos and black beans.",
      "course": "salad",
      "price": 1.82
    }
  ]
}

---

通用模型

struct ApiResponseGeneric<T> : Content where T: Content { 
    var links: Links?
    var data: T
    
    init(links: Links, data: T) {
        self.links = links
        self.data = data
    }
}

具体路线端点

router.post(Dish.self, at: "api/dish-generic-future") { 
    (request: Request, dish: Dish) -> Future<ApiResponseGeneric<[Dish]>> in
    var dishMutable = dish
    dishMutable.id = 004
    
    var links = Links()
    links.current = "http://example.com"
    links.next = "http://example.com"
    links.last = "http://example.com"
    
    return Future.map(on: request, { 
        () -> ApiResponseGeneric<[Dish]> in
        return ApiResponseGeneric<[Dish]>(links: links, data: [dishMutable])
    }) 
}