《精通 iOS 开发》第 06 章学习笔记

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延迟加载处理

代码示例：

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- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  self.blueViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"Blue"];
  [self.view insertSubview:self.blueViewController.view atIndex:0];
}

内存不足处理

代码示例：

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- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
  if (!self.blueViewController.view.superview) {
    self.blueViewController = nil;
  } else {
    self.yellowViewController = nil;
  }
}

转换过程的动画效果

代码示例：

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- (IBAction)switchViews:(id)sender {
  [UIView beginAnimations:@"View Flip" context:NULL];
  [UIView setAnimationDuration:0.4];
  [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

  if (!self.yellowViewController.view.superview) {
    if (!self.yellowViewController) {
      self.yellowViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"Yellow"];
    }

    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];

    [self.blueViewController.view removeFromSuperview];
    [self.view insertSubview:self.yellowViewController.view atIndex:0];
  } else {
    if (!self.blueViewController) {
      self.blueViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"Blue"];
    }

    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES];

    [self.yellowViewController.view removeFromSuperview];
    [self.view insertSubview:self.blueViewController.view atIndex:0];
  }

  [UIView commitAnimations];
}