方法一:
- +(SchoolManager *)sharedInstance
- {
- static SchoolManager *sharedManager;
- static dispatch_once_t onceToken;
- dispatch_once(&onceToken, ^{
- sharedManager = [[SchoolManager alloc] init];
- });
- return sharedManager;
- }
方法二:配置後利用dispatch_onceToken實現:
配置:allocWithZone和copyWithZone要覆蓋調父類的,
// .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; \
}\
- (id)copyWithZone:(NSZone *)zone \
{ \
return _instance; \
}
使用:
Manager.h文件
#import <Foundation/Foundation.h>
@interface Manager :NSObject
singleton_interface(Manager);
@end
Manager.m文件
#import "Manager.h"
@interface Manager ()
@end
@implementation Manager
singleton_implementation(Manager)
@end
viewController調用
Manager *manager = [Manager sharedManager];
方法三:先判斷有沒有這個對象,沒有就創建。