如何将“(Data?, URLResponse, Error?)”转换为预期的参数类型“(Data?, URLResponse?, Error?) -> Void”

Question

我不明白为什么我在这一行中遇到 { 错误。让任务 = URLSession

let task = URLSession.shared.dataTask(with: request) { (data: Data?, response: URLResponse, error: Error?) in   //ERROR: Cannot convert value of type '(Data?, URLResponse, Error?) -> ()' to expected argument type '(Data?, URLResponse?, Error?) -> Void'

        self.removeActivityIndicator(activitiyIndicator: myActivityIndicator)

        if error != nil {
            self.displayMessage(userMessage: "Could not successfully perform this request")
            print("error=\(String(describing: error))")
            return
        }

        do {
            let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary

如有任何建议，我们将不胜感激。

Answer 1

请仔细阅读错误，它说第二个闭包参数(URLResponse)必须是可选的(URLResponse?)

let task = URLSession.shared.dataTask(with: request) { (data: Data?, response: URLResponse?, error: Error?) in

但是不需要注释参数类型

let task = URLSession.shared.dataTask(with: request) { data, response, error in

如果您错误地对待（可选）类型，编译器会报错。

并且不要在 Swift 中使用 NS.. 集合类型。使用本机类型。

如何将“(Data?, URLResponse, Error?)”转换为预期的参数类型“(Data?, URLResponse?, Error?) -> Void”

How to convert '(Data?, URLResponse, Error?) to expected argument type '(Data?, URLResponse?, Error?) -> Void'

xcode

swift

swift5