转换具有通用 class 签名 swift 的具体类型

Question

I have a struct like this

struct ApiResponse<T: Codable>: Codable {
 let result: T?
 let statusCode: String?
}

Somewhere in my code I need statusCode . I am not interested in result but Swift is not allowing me to use following:

let apiResponse = value as? ApiResponse

it shows following error:

Generic parameter 'T' could not be inferred in cast to 'ApiResponse'

which is quite obvious since struct definition ask some struct conforming to Codable but at same time i can not use one type as it will fail for other types.

eg

let apiResponse = value as? ApiResponse<ApiResult> 

would be true for one type of response but if i have ApiResponse<ApiOtherResult> it will fail.

        NetworkLayer.requestObject(router: router) { (result: NetworkResult<T>) in

        switch result {
        case .success(let value):
            if let apiResponse = value as? ApiResponse {
                }
        case .failure: break
        }

    }

Answer 1

I'd suggest adding a new protocol

protocol StatusCodeProvider {
    var statusCode: String? { get }
}

Add it as a requirement in your function making sure that T in NetworkResult<T> conforms to StatusCodeProvider and add conformance for every T you want to request.