Question

我试图创建一个包含API请求的响应库，但是使用可编码时出现错误Non-nominal type 'T' does not support explicit initialization。这曾经与第三方库一起使用，但是我将旧数据换成了新数据。

class ResponseBase: Codable {
    var status: String?
    var message: String?
    var pagination: Pagination?

    var isSucessful: Bool {
        return status == "success"
    }

    struct ErrorMessage {
        static let passwordInvalid = " Current password is invalid."
        static let loginErrorIncorrectInfo = " Incorrect username/password."
        static let loginErrorAccountNotExist = " Invalid request"
    }
}

class Response<T: Codable>: ResponseBase {
    var data: T?

    public func setGenericValue(_ value: AnyObject!, forUndefinedKey key: String) {
        switch key {
        case "data":
            data = value as? T
        default:
            print("---> setGenericValue '\(value)' forUndefinedKey '\(key)' should be handled.")
        }
    }

    public func getGenericType() -> Codable {
        return T()
    }
}

Answer 1

public func getGenericType() -> T.Type {
    return T.self
}

Answer 2

该错误消息表示它的意思。仅符合Codable并不能保证init存在，因此说T()是非法的。您必须自己做出保证。例如：

protocol CodableAndInitializable : Codable {
    init()
}
class ResponseBase: Codable {
    // ....
}
class Response<T: CodableAndInitializable>: ResponseBase {
    var data: T?
    // ....
    public func getGenericType() -> Codable {
        return T()
    }
}

非标称类型“ T”不支持显式初始化

2 个答案: