iOS 视图控制器的内存申请与释放普遍规则

小记 iOS 视图控制器的内存申请与释放普遍规则

作者:不及格的程序员-八神

内存管理在iOS程序开发扮演非常重要角色,对这块处理不好的程序会在实际设备上发生Crash情况.
对于经常在视图控制器中用retain声名的输出口一定要注意,在dealloc中release它们.
Obj-C声明的属性,具有如下特性,将新对象赋值当前属性,并自动释放属性中的旧对象.

在appDelegate.m中如果有一个window输出口,或者另外加了一个导航视图控制器或是其它什么视图控制器时,在 dealloc 方法中,执行这些输出口的release方法.而不必在applicationDidFinishLaunching中执行释放.

在单独的自定义视图控制器中,如果在接到内存紧缺通知时,会执行didReceiveMemoryWarning方法,它会卸载当前视图窗体,并执行viewDidUnload方法,所以在该方法中将方视图中的定义的输出口置为nil. 同时在该视图的dealloc方法(当该视图控件器的release被调用时,该方法被执行)中执行相应的输出口release方法.



-(void)viewDidUnload
{
self.**= nil;
}

-(void)dealloc
{
[** release];
[supper dealloc];
}



实例方法,静态方法,工厂方法返回的对象的释方规则,后两者都不必手动执行release方法,由系统的内存池自动维护.

如果我在appDelegate.m文件中alloc并init一个视图控制器,然后把它通过导航控制器的initWithRootViewController方法加到其中时,那么加完之后要释放那个视图控制器.Example:　　

myController = [[*** alloc] initWithNibName:"***" bundle:nil];
UINavigationController *navi = [[UINavigationController alloc] initWithRootViewController:myController];
[myController release];
[tabController presentModalViewController:navi animated:YES];
[navi release];

在自定义视图控制器中声明了变量,但是没定义相应属性,这时对象释放规则同第1条相同.



@interface *** : UIViewController
{
UIView *_view;
}
@end

@implementation ***
-(void)loadView
{
[supper loadView];
_view = [[UIView alloc] initWithFrame:[self.view bounds]];
[self.view addSubview:_view];
}

-(void)dealloc
{
[_view release];
[supper dealloc];
}
@end



在iPhone3开发基础教程中的样例切换视图的代码问题,我觉得里面有一个顺序写错了,之后我在google查了一下,有不少人有同问.



@implementation SwitchViewController
@synthesize blueViewController;
@synthesize yellowViewController;

- (void)viewDidLoad
{
BlueViewController *blueController = [[BlueViewController alloc] initWithNibName:@"BlueView" bundle:nil];
self.blueViewController = blueController;
[self.view insertSubview:blueController.view atIndex:0];
[blueController release];
}

- (IBAction)switchViews:(id)sender
{
[UIView beginAnimations:@"View Flip" context:nil];
[UIView setAnimationDuration:1.25];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

if (self.yellowViewController.view.superview == nil)//这条语句是最有趣的,OBJ-C允许向nil发送消息.
{
if (self.yellowViewController == nil)
{
YellowViewController *yellowController =
[[YellowViewController alloc] initWithNibName:@"YellowView"
bundle:nil];
self.yellowViewController = yellowController;
[yellowController release];
}
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];
[blueViewController viewWillAppear:YES];
[yellowViewController viewWillDisappear:YES];
[blueViewController.view removeFromSuperview];
[self.view insertSubview:yellowViewController.view atIndex:0];
[yellowViewController viewDidDisappear:YES];
[blueViewController viewDidAppear:YES];
}
else
{
if (self.blueViewController == nil)
{
BlueViewController *blueController =
[[BlueViewController alloc] initWithNibName:@"BlueView"
bundle:nil];
self.blueViewController = blueController;
[blueController release];
}
//[UIView setAnimationTransition:
// UIViewAnimationTransitionFlipFromLeft
// forView:self.view cache:YES];

//[yellowViewController viewWillAppear:YES];
//[blueViewController viewWillDisappear:YES];
[yellowViewController.view removeFromSuperview];
[self.view insertSubview:blueViewController.view atIndex:0];
//[blueViewController viewDidDisappear:YES];
//[yellowViewController viewDidAppear:YES];
}
//[UIView commitAnimations];
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
if (self.blueViewController.view.superview == nil)
self.blueViewController = nil;
else
self.yellowViewController = nil;
}

- (void)dealloc
{
[yellowViewController release];
[blueViewController release];
[super dealloc];
}

@end



都在dealloc中执行.我看到在wordPress的iPhone客户端这样做的,不过好像它在特意兼容iOS3之前的版本,3.0之前的版本并不存在viewDidUnload方法,苹果的开发手册上有描述.

-(void)dealloc
{
[myView release], myView = nil;
}

附.
python /Users/yangiori/Downloads/facebook-three20-309d34e/src/scripts/ttmodule.py -p /Users/yangiori/Documents/iPhoneLiaoBao/iPhoneLiaoBao.xcodeproj Three20 //区分大小写。。。