为什么我收到此错误：对成员'fetch（with：parse：completion :)'的模糊引用

Question

我正在使用 Xcode 8.3.3 。我收到 Swift 编译器错误“对成员的不明确引用”。我已经完成了代码，似乎无法弄明白。

protocol APIClient {
var session: URLSession { get }
func fetch<T: JSONDecodable>(with request: URLRequest, parse: @escaping (JSON) -> T?, completion: @escaping (Result<T, APIError>) -> Void)

    func fetch<T: JSONDecodable>(with request: URLRequest, parse: @escaping (JSON) -> [T], completion: @escaping (Result<[T], APIError>) -> Void)
}
fetch(with: request, parse: { json -> [YelpBusiness] in
            guard let businesses = json["businesses"] as? [[String: Any]] else { return [] }
            return businesses.flatMap { YelpBusiness(json: $0) }
}, completion: completion)

https://github.com/jripke74/RestaurantReviews.git

Answer 1

我检查了你的代码。您已创建protocol来确认班级YelpClient。怎么了？

fetch(with: request, parse: { json -> [YelpBusiness] in
            guard let businesses = json["businesses"] as? [[String: Any]] else { return [] }
            return businesses.flatMap { YelpBusiness(json: $0) }
}, completion: completion)

使用上面的代码，您可以直接拨打protocol而无需任何delegate。问题是您需要继承protocol类中的YelpClient，如下所示。

func fetch<T>(with request: URLRequest, parse: @escaping (APIClient.JSON) -> T?, completion: @escaping (Result<T, APIError>) -> Void) where T : JSONDecodable {
    //Code
}

func fetch<T>(with request: URLRequest, parse: @escaping (APIClient.JSON) -> [T], completion: @escaping (Result<[T], APIError>) -> Void) where T : JSONDecodable {
    //Code
}

有关详细信息，请参阅apple documentation

  

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