1 。 宏写法
// .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.自写
+ (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;
}
