swift - 使用泛型组合 2 个独立的几乎相同的函数

Question

我有 2 个函数用于在一些网络代码上提供一个层。

历史上只有 1 个函数，但我刚刚坐下来扩展它并意识到除了某些类型之外它们是相同的。

是否可以使用泛型将它们结合起来？

或者是过度杀戮？

我读了一些书，正在努力理解如何在这里实现泛型

func profile(with endpoint: ProfilesEndpoint, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<ProfileResponse>) -> Void) {
    var request = endpoint.request
    request.httpMethod = method.rawValue

    if let body = body {
        request.httpBody = body.data(using: .utf8)
    }

    if let headers = headers {
        for (key, value) in headers {
            request.addValue(value, forHTTPHeaderField: key)
        }
    }

    execute(with: request, completion: completion)
}

func identity(with endpoint: IdentityEndpoint, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<OAuthTokenResponse>) -> Void) {
    var request = endpoint.request
    request.httpMethod = method.rawValue

    if let body = body {
        request.httpBody = body.data(using: .utf8)
    }

    if let headers = headers {
        for (key, value) in headers {
            request.addValue(value, forHTTPHeaderField: key)
        }
    }

    execute(with: request, completion: completion)
}

我已经尝试过，但收到一个错误，提示 Value of type 'T' has no member 'request'

func request<T: Comparable, X: Comparable>(with endpoint: T, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<X>) -> Void) {
    var request = endpoint.request
    request.httpMethod = method.rawValue

    if let body = body {
        request.httpBody = body.data(using: .utf8)
    }

    if let headers = headers {
        for (key, value) in headers {
            request.addValue(value, forHTTPHeaderField: key)
        }
    }

    execute(with: request, completion: completion)
}

Answer 1

你得到那个错误是因为不是所有类型都有这个名为 request 的变量.泛型不适合这个问题，因为你指的是一个特定的类(它不是通用的)。

这里有两个想法可以解决您的问题:

方法1-

我认为这是最好的选择，因为它很直观 - 每个函数都有自己的目的和描述，同时代码循环使用并保持简单

改变

func request<T: Comparable, X: Comparable>(with endpoint: T, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<X>) -> Void)

到

private func request(urlRequest: URLRequest, method: HTTPMethod, body: String? , headers: [String: String]?, completion: @escaping (response: HttpResponse) -> Void)

然后从profile(...)和 identity(...)你可以调用你的请求函数-

func profile(with endpoint: ProfilesEndpoint, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<ProfileResponse>) -> Void) {
    var urlRequest = endpoint.request
    // call request(urlRequest: urlRequest, ...) and handle completion
}

func identity(with endpoint: IdentityEndpoint, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either< OAuthTokenResponse>) -> Void) {
    var urlRequest = endpoint.request
    // call request(urlRequest: urlRequest, ...) and handle completion 
}

private func request(urlRequest: URLRequest, method: HTTPMethod, body: String? , headers: [String: String]?, completion: @escaping (response: HttpResponse) -> Void){ 

    var request = urlRequest
    .
    .
    .
 }

方法2-

创建一个名为 Endpoint 的协议(protocol)，并在 ProfileEndpoint 和 IdentityEndpoint 上实现它。

protocol Endpoint{
    var request: URLRequest { get }
}

class ProfilesEndpoint: Endpoint {
    // this class must contain variable request because it implements Endpoint protocol
    var request: URLRequest{
        .
        .
        return ...
    }
}
class IdentityEndpoint: Endpoint {
    // this class must contain variable request because it implements Endpoint protocol
    var request: URLRequest{
        .
        .
        return ...
    }
}

然后你可以把你的请求函数改成-

(我真的不熟悉Either<>所以我不确定你的完成情况)

func request(with endpoint: Endpoint, method: HTTPMethod, body: String?, headers: [String: String]?, completion: @escaping (Either<X>) -> Void) {

    var request = endpoint.request
    request.httpMethod = method.rawValue

    if let body = body {
        request.httpBody = body.data(using: .utf8)
    }

    if let headers = headers {
        for (key, value) in headers {
            request.addValue(value, forHTTPHeaderField: key)
        }
    }

    execute(with: request, completion: completion)
}

您可以使用 IdentityEndpoint 调用此函数或 ProfilesEndpoint因为它们都符合 protocol Endpoint - 谁声明了变量request ，所以可以肯定的是，这两个类也会有这个变量。