我正在向后端发送 POST 请求，并在启动到下一个 View Controller 的 segue 之前等待响应。执行此操作的最佳方法是什么 - 带有完成处理程序的异步 block ？如果 POST 请求返回某个值，则应用程序应跳转到下一个 View Controller ，如果响应是错误，则不应发生任何跳转。
@IBAction func finishPressed(sender: AnyObject) {
if self.emailField.text != "" && self.usernameField.text != "" && self.passwordField.text != ""
{
var dict = ["email": emailField.text, "username": usernameField.text, "password_hash": passwordField.text]
self.register2(dict, completion: { (result) -> Void in
if (result == true)
{
self.performSegueWithIdentifier("homeView", sender: nil)
}
else
{
print("can't segue")
}
})
}
func register(params: Dictionary<String, String!>, completion: (result:Bool) -> Void))
{
//Request set up and configuration
var json = NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves, error: &err) as? NSDictionary
if(err != nil)
{
print(err!.localizedDescription)
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
completion(result: true)
}
else {
if let parseJSON = json {
var success = parseJSON["success"] as? Int
var usernameError = parseJSON["usernameError"] as? String
var emailError = parseJSON["emailError"] as? String
if success == 1
{
print("we have Success: \(success)")
completion(result: true)
}
else
{
print("we have Failure: \(success)")
completion(result: false)
}
else {
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: \(jsonStr)")
completion(result: false)
}
}
})
task.resume()
}
编辑:我在代码中添加了一个完成处理程序，但在尝试继续时崩溃了
*** Assertion failure in -[UIKeyboardTaskQueue waitUntilAllTasksAreFinished]
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIKeyboardTaskQueue waitUntilAllTasksAreFinished] may only be called from the main thread.'
最佳答案
看起来完成处理程序是从非主线程的线程调用的。要确保完成处理程序在主线程上执行，请将对完成处理程序的调用包装在在主线程上执行的 gcd block 内:
dispatch_async(dispatch_get_main_queue()) {
completion(result:true)
}
关于ios - POST 请求响应后启动 segue，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32127973/