使Vapor API响应符合JSON API规范

Question

我有一个用Vapor编写的API。我想按照JSON API规范。

我正在努力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此......

{
  "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到此端点，我可以非常简单地返回数据的内容（伪代码）

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，以便我可以构建响应，但这不适用于错误Cannot convert return expression of type 'ApiResonse' to return type 'Dish'

   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)
        })
    }

我不知道怎么能这样做。这些是尝试过的课程

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？有人能提供一个例子吗？

Answer 1

1. 复合物体class中的每个struct或ApiResponse都需要符合Content协议。 Content协议包括用于JSON解码和编码的Codable协议。
2. 请注意，Any不符合Codable协议，因此Any不能用作Response的任何组成部分。有关更多详细信息，请参阅Vapor Docs: "Using Content"。 在Vapor 3中，所有内容类型（JSON，protobuf，URLEncodedForm，Multipart等）都被视为相同。解析和序列化内容所需的只是一个Codable类或结构。
3. 完全符合Content的物体或复合物体可用作ResponseEncodable响应。
4. 当每个路由端点解析为特定的ApiResponse协议兼容类型时，Content模型可以是通用的。

以下代码的示例项目位于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Response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
    }
}

具体路线终点

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])
    }) 
}

Answer 2

你需要让data成为[Dish]

class ApiResonse {
    var links: Links?
    var data: [Dish]

    init(links: Links, data: [Dish]) {
        self.links = links
        self.data = [Dish]
    }
}