ios - 尝试 - 抛出 IBAction - xCode 7

Question

我对新的“throws”-“try”参数有疑问。

我在添加这些词时遇到错误，因此我在 IBAction 函数的末尾添加了“throws”。

@IBAction func loginButtonPressed(sender: AnyObject)throws {//code here}

我在里面做一些不相关的东西，然后是这个:

let jsonData:NSDictionary = try NSJSONSerialization.JSONObjectWithData(urlData!, options:NSJSONReadingOptions.MutableContainers ) as! NSDictionary

之后没有错误，但是当我运行应用程序并单击按钮时，应用程序崩溃并显示代码

2015-06-15 10:43:11.374 BottLED[7283:1175818] -[BottLED.loginViewController loginButtonPressed:]: unrecognized selector sent to instance 0x7fee28da7d20 2015-06-15 10:43:11.381 BottLED[7283:1175818] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[BottLED.loginViewController loginButtonPressed:]: unrecognized selector sent to instance 0x7fee28da7d20' * First throw call stack: ( 0 CoreFoundation 0x000000010d67c885 exceptionPreprocess + 165 1 libobjc.A.dylib 0x000000010cd0edf1 objc_exception_throw + 48 2 CoreFoundation 0x000000010d684b5d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205 3 CoreFoundation 0x000000010d5d1e3a ___forwarding_ + 970 4 CoreFoundation 0x000000010d5d19e8 _CF_forwarding_prep_0 + 120 5 UIKit 0x000000010dc46257 -[UIApplication sendAction:to:from:forEvent:] + 125 6 UIKit 0x000000010dc461b2 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 79 7 UIKit 0x000000010dda1422 -[UIControl sendAction:to:forEvent:] + 67 8 UIKit 0x000000010dda16c6 -[UIControl _sendActionsForEvents:withEvent:] + 272 9 UIKit 0x000000010dda08a9 -[UIControl touchesEnded:withEvent:] + 599 10 UIKit 0x000000010dcacbe8 -[UIWindow _sendTouchesForEvent:] + 835 11 UIKit 0x000000010dcad7d6 -[UIWindow sendEvent:] + 865 12 UIKit 0x000000010dc62705 -[UIApplication sendEvent:] + 263 13 UIKit 0x000000010dc3f5df _UIApplicationHandleEventQueue + 6031 14 CoreFoundation 0x000000010d5a70f1 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 17 15 CoreFoundation 0x000000010d59ceac __CFRunLoopDoSources0 + 556 16 CoreFoundation 0x000000010d59c363 __CFRunLoopRun + 867 17 CoreFoundation 0x000000010d59bd78 CFRunLoopRunSpecific + 488 18 GraphicsServices 0x0000000111fdebca GraphicsServices + 52170 19 UIKit 0x000000010dc4479b UIApplicationMain + 171 20 BottLED 0x000000010c7cb9ad main + 109 21 libdyld.dylib 0x000000011029ca05 libdyld.dylib + 10757 22 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

当我做一些断点并删除“throws”时，应用程序不会崩溃。我现在真的不知道该怎么办..我希望有人能帮助我!

完整代码为:

@IBAction func loginButtonPressed(sender: AnyObject)throws {
    var name:NSString = textFieldName.text!
    let pass:NSString = textFieldPw.text!
    if ( name.isEqualToString("") || pass.isEqualToString("") ) {
        let loginFailed = UIAlertView(title: "Failed to Signup",
            message: "Please fill in all Textfields",
            delegate: nil,
            cancelButtonTitle: "OK")
        loginFailed.show()
    } else {

            let post:NSString = "username=\(name)&password=\(pass)"

            NSLog("PostData: %@",post);

            let url:NSURL = NSURL(string: "my url")!

            let postData:NSData = post.dataUsingEncoding(NSASCIIStringEncoding)!

            let postLength:NSString = String( postData.length )

            let request:NSMutableURLRequest = NSMutableURLRequest(URL: url)
            request.HTTPMethod = "POST"
            request.HTTPBody = postData
            request.setValue(postLength as String, forHTTPHeaderField: "Content-Length")
            request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
            request.setValue("application/json", forHTTPHeaderField: "Accept")


            var reponseError: NSError?
            var response: NSURLResponse?

            var urlData: NSData?
            do {
                urlData = try NSURLConnection.sendSynchronousRequest(request, returningResponse:&response)
            } catch let error as NSError {
                reponseError = error
                urlData = nil
            }

            if ( urlData != nil ) {
                let res = response as! NSHTTPURLResponse!;

                NSLog("Response code: %ld", res.statusCode);

                if (res.statusCode >= 200 && res.statusCode < 300)
                {
                    let responseData:NSString  = NSString(data:urlData!, encoding:NSUTF8StringEncoding)!

                    NSLog("Response ==> %@", responseData);



                    let jsonData:NSDictionary = try NSJSONSerialization.JSONObjectWithData(urlData!, options:NSJSONReadingOptions.MutableContainers ) as! NSDictionary


                    let success:NSInteger = jsonData.valueForKey("success") as! NSInteger

                    //[jsonData[@"success"] integerValue];

                    NSLog("Success: %ld", success);

                    if(success == 1)
                    {

Answer 1

在 Obj-C 中 throws 是 Obj-C error: (NSError **)error 参数的语法糖。

当你向一个方法添加throws时，它就 secret 地添加了参数。你的方法将不再是 loginButtonPressed: ，它将是 loginButtonPressed:error: (至少对于 Obj-C 来说)。然而，当事件被处理时，系统仍然会寻找方法loginButtonPressed:，因为这就是事件在XIB中的连接方式。该方法不再存在，因此应用程序将崩溃，并无法识别的选择器发送到实例。

解决方案:不要在操作处理程序中使用throws，它违反了方法的约定，因为系统不希望在那里抛出任何东西。在您的操作处理程序中捕获所有错误。

do {
    urlData = try NSURLConnection.sendSynchronousRequest(request, returningResponse:&response)
} catch let error as NSError {
    reponseError = error
    urlData = nil
} catch {
   // Catch all error-handling
    urlData = nil
}