檢測最後視圖UIViewController

Question

我想編程一個頁面，以便當我點擊'返回'按鈕時，我得到了最後訪問的UIViewController。

末頁代碼：

[[NSUserDefaults standardUserDefaults] setObject:NSStringFromClass([self class]) forKey:@"currentViewController"]; 
[[NSUserDefaults standardUserDefaults] synchronize]; 

返回按鈕代碼：

- (IBAction)Return:(id)sender { 
     NSString *savedClassName = [[NSUserDefaults standardUserDefaults] objectForKey:@"currentViewController"]; 
UIViewController *screen = (UIViewController *)NSClassFromString(savedClassName); 
screen.modalTransitionStyle = UIModalTransitionStyleCrossDissolve; 
[self presentModalViewController:screen animated:YES]; 
      } 

問題是，它不斷返回錯誤：

+[SAVEDVIEWNAME setModalTransitionStyle:]: unrecognized selector sent to class 0x59b98 
2013-12-14 12:47:27.462 Friends+[16358:a0b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[Calander setModalTransitionStyle:]: unrecognized selector sent to class 0x59b98' 

我明白它要表達的意思，但這沒有意義，因爲在這種情況下，這是完全可以接受的！

任何幫助表示讚賞thnx。

Answer 1

你需要從類實例化一個objcet，就像這樣：

NSString *savedClassName = [[NSUserDefaults standardUserDefaults] objectForKey:@"currentViewController"]; 
Class cls = NSClassFromString(savedClassName); 
UIViewController *screen = (UIViewController *)[cls new]; 
screen.modalTransitionStyle = UIModalTransitionStyleCrossDissolve; 
[self presentViewController:screen animated:YES completion:nil]; //You should use this instead of presentModalViewController:animated: !