iOS中单例的通用写法(在ARC, MRC下可用)，增加了单线程访问限制。
LASingletonPattern.h
#import <Foundation/Foundation.h>
@interface LASingletonPattern : NSObject <NSCopying>
+ (instancetype)shareInstance;
@end
LASingletonPattern.m
#import "LASingletonPattern.h"
@implementation LASingletonPattern
static id _instance;
+ (instancetype)allocWithZone:(struct _NSZone *)zone {
if (_instance == nil) {
@synchronized (self) {
if (_instance == nil) {
_instance = [super allocWithZone:zone];
}
}
}
return _instance;
}
+ (instancetype)shareInstance {
if (_instance == nil) {
@synchronized (self) {
if (_instance == nil) {
_instance = [[self alloc] init];
}
}
}
return _instance;
}
#pragma mark - 重写MRC相关方法
- (oneway void)release {
}
- (instancetype)retain {
return _instance;
}
- (NSUIntegers)retainCount {
return 1;
}
- (instancetype)autorelease {
return _instance;
}
- (id)copyWithZone:(NSZone *)zone {
return _instance;
}
@end
