iOS设计模式 - 单例
原理图
说明
1. 单例模式人人用过,严格的单例模式很少有人用过
2. 严格的单例模式指的是无法通过常规的 alloc init 方法来生成对象,派生出来的子类也不能产生出对象,而只能通过单例的方法获取到对象
源码
https://github.com/YouXianMing/iOS-Design-Patterns
//
// Singleton.h
// SingletonPattern
//
// Created by YouXianMing on 15/8/6.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface Singleton : NSObject
+ (Singleton *)sharedInstance;
@end//
// Singleton.m
// SingletonPattern
//
// Created by YouXianMing on 15/8/6.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
//
#import "Singleton.h"
#define STR_SINGLETON @"STR_SINGLETON"
static Singleton *_sharedSingleton = nil;
@implementation Singleton
+ (Singleton *)sharedInstance {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_sharedSingleton = (Singleton *)STR_SINGLETON;
_sharedSingleton = [[Singleton alloc] init];
});
return _sharedSingleton;
}
- (instancetype)init {
NSString *string = (NSString *)_sharedSingleton;
if ([string isKindOfClass:[NSString class]] && [string isEqualToString:STR_SINGLETON]) {
self = [super init];
if (self) {
}
return self;
} else {
return nil;
}
}
@end细节
保证只能从shareInstance方法获取实例的技巧
