1 。 宏寫法
// .h
#define singleton_interface(class) + (instancetype)shared##class;
// .m
#define singleton_implementation(class) \
static class *_instance; \
\
+ (id)allocWithZone:(struct _NSZone *)zone \
{ \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instance = [super allocWithZone:zone]; \
}); \
\
return _instance; \
} \
\
+ (instancetype)shared##class \
{ \
if (_instance == nil) { \
_instance = [[class alloc] init]; \
} \
\
return _instance; \
}
2.自寫
+ (instancetype)sharedInstance
{
static?dispatch_once_t?__singletonToken;
static?id?__singleton__;
dispatch_once(?&__singletonToken,?^{?__singleton__?=?[[self?alloc]?init];?}?);
return__singleton__;
}
+ (YYVersionAgent *)sharedInstance
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[YYVersionAgent alloc] init];
});
return sharedInstance;
}
