1、应用程序委托对象
在应用程序委托对象中接收内存警告消息，需要重写applicationDidReceiveMemoryWarning:方法。AppDelegate的代码片段：
- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
{
NSLog(@”AppDelegate中调用applicationDidReceiveMemoryWarning:”);
}
2、视图控制器
在视图控制器中接收内存警告消息，需要重写didReceiveMemoryWarning方法。ViewController的代码片段：
- (void)didReceiveMemoryWarning
{
NSLog(@”ViewController中didReceiveMemoryWarning调用”);
[super didReceiveMemoryWarning];
//释放成员变量
[_listTeams release];
}
注意释放资源代码应该放在[super didReceiveMemoryWarning]语句下面。
3、其它类
在其它类中可以使用通知，在内存警告时候iOS系统会发出UIApplicationDidReceiveMemoryWarningNotification通知，凡是在通知中心注册了
UIApplicationDidReceiveMemoryWarningNotification通知的类都会接收到内存警告通知。ViewController的代码片段：
- (void)viewDidLoad
{
[super viewDidLoad];
NSBundle *bundle = [NSBundle mainBundle];
NSString *plistPath = [bundle pathForResource:@"team"
ofType:@"plist"];
//获取属性列表文件中的全部数据
NSArray *array = [[NSArray alloc] initWithContentsOfFile:plistPath];
self.listTeams = array;
[array release];
//接收内存警告通知，调用handleMemoryWarning方法处理
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self
selector:@selector(handleMemoryWarning)
name:UIApplicationDidReceiveMemoryWarningNotification
object:nil];
}
//处理内存警告
-(void) handleMemoryWarning
{
NSLog(@”ViewController中handleMemoryWarning调用“);
}
我们在viewDidLoad方法中注册UIApplicationDidReceiveMemoryWarningNotification消息，接收到报警信息调用handleMemoryWarning方法。这些代码完全可以写在其它类中，在ViewController中重写didReceiveMemoryWarning方法就可以了，本例这是示意性介绍一下UIApplicationDidReceiveMemoryWarningNotification报警消息。
内存警告在设备上出现并不是经常的，一般我们没有办法模拟，但模拟器上有一个功能可以模拟内存警告，启动模拟器，选择模拟器菜单硬件→模拟内存警告，这个时候我们会在输出窗口中看到内存警告发生了。
2012-11-06 16:49:16.419 RespondMemoryWarningSample[38236:c07] Received memory warning.
2012-11-06 16:49:16.422 RespondMemoryWarningSample[38236:c07] AppDelegate中调用applicationDidReceiveMemoryWarning:
2012-11-06 16:49:16.422 RespondMemoryWarningSample[38236:c07] ViewController中handleMemoryWarning调用
2012-11-06 16:49:16.423 RespondMemoryWarningSample[38236:c07] ViewController中didReceiveMemoryWarning调用
