http://blog.csdn.net/mars2639/article/details/7283741
static Singleton * sharedInstance = nil;
@implementation Singleton
//获取单例
+(Singleton *)sharedInstanceMethod
{
@synchronized(self) {
if (sharedInstance == nil)
sharedInstance = [[self alloc] init];
}
}
return sharedInstance;
}
//唯一一次alloc单例，之后均返回nil
+ (id)allocWithZone:(NSZone *)zone
{
@synchronized(self) {
if (sharedInstance == nil) {
instance = [super allocWithZone:zone];
return instance;
}
}
return nil;
}
//copy返回单例本身
- (id)copyWithZone:(NSZone *)zone
{
return self;
}
//retain返回单例本身
- (id)retain
{
return self;
}
//引用计数总是为1
- (unsigned)retainCount
{
return 1;
}
//release不做任何处理
- (void)release
{
}
//autorelease返回单例本身
- (id)autorelease
{
return self;
}
//
-(void)dealloc
{
[super dealloc];
}
@end
ios5 有了arc以后就这样简单
static RootViewController* sharedRootController = nil; +(RootViewController *) sharedController{ @synchronized(self){ if (sharedRootController == nil) { sharedRootController = [[self alloc] init]; } } return singleController; }
还有一种方法
static AccountManager *sharedAccountManagerInstance = nil;
static dispatch_once_t predicate;
dispatch_once(&predicate, ^{
sharedAccountManagerInstance = [[self alloc] init];
});
return sharedAccountManagerInstance;