检查是否UIViewController中已经创建

Question

我想检查一个视图控制器已创建。如果视图已经存在，那么它应该成为当前视图。如果它不存在，则应该创建并使其可见。

我的代码是

  DemoViewController *demoController = [DemoViewController alloc]; 
     for(DemoViewController *view in self.navigationController.viewControllers) 
     { 
      if([view isKindOfClass:[DemoViewController class]]) 
      { 
       viewExists=true; 
       demoController=view; 
      } 

     } 
     if (!viewExists) { 
      demoController initWithNibName:@"DemoViewController" bundle:nil; 
     } 
     [view release]; 
     [demoController release]; 

我不知道我要去哪里错了，但它会出现在for循环没有被执行。 任何帮助将是伟大的！

Answer 1

尝试这样的：

DemoViewController* demoController = nil; 
for(int vv=0; vv<[self.navigationController.viewControllers count]; ++vv) { 
    NSObject *vc = [self.navigationController.viewControllers objectAtIndex:vv]; 
    if([vc isKindOfClass:[DemoViewController class]]) { 
     demoController = (DemoViewController*)vc; 
    } 
} 

if (demoController == nil) { 
    demoController = [[DemoViewController alloc] initWithNibName:@"DemoViewController" bundle:nil]; 
    // Do we need to push it into navigation controller? 
} 

[demoController release];