Swift 4 在完成处理程序中访问 textView

Question

Swift 4. 在完成处理程序中附加 UITextView 时遇到问题。错误和崩溃是它只能从主线程访问。提前致谢。

    let jsonUrlString = "http://192.168.1.5:8080/users"
    guard let url = URL(string: jsonUrlString) else {return}

    URLSession.shared.dataTask(with: url) { (data, response, err) in

        guard let data = data else { return}

        let dataAsString = String(data: data, encoding: .utf8) ?? "No data received"
        print(dataAsString)

        do {
           self.userList = try

                JSONDecoder().decode([User].self, from: data)

            for usr in self.userList {
                    print(usr.username)
                self.textView!.text.append(usr.username)
                }
        } catch let jsonErr {
            print("error serializing json: ", jsonErr)
        }

    }.resume()
}

Answer 1

你可以试试

DispatchQueue.main.async { 
  self.textView!.text.append(usr.username) 
}

或者

self.userList = try   JSONDecoder().decode([User].self, from: data)
DispatchQueue.main.async {
   self.textView!.text = self.userList.map{$0.username}.joined(separator:"")
}