iOS设计模式 - 备忘录
原理图
说明
1. 在不破坏封装的情况下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样以后就可以将该对象恢复到原先保存的状态
2. 本人已经将创建状态与恢复状态的逻辑抽象成了协议，并配合备忘录中心一起使用
源码
https://github.com/YouXianMing/iOS-Design-Patterns
//
// MementoCenter.h
// MementoPattern
//
// Created by YouXianMing on 15/9/11.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
// #import <Foundation/Foundation.h>
#import "MementoCenterProtocol.h" @interface MementoCenter : NSObject /**
* 存储备忘录对象
*
* @param mementoObject 备忘录对象
* @param key 标记对象的键值
*/
+ (void)saveMementoObject:(id <MementoCenterProtocol>)mementoObject withKey:(NSString *)key; /**
* 获取备忘录对象
*
* @param key 标记对象的键值
*
* @return 备忘录对象
*/
+ (id)mementoObjectWithKey:(NSString *)key; @end
//
// MementoCenter.m
// MementoPattern
//
// Created by YouXianMing on 15/9/11.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
// #import "MementoCenter.h"
#import "FastCoder.h"
#import <CommonCrypto/CommonDigest.h> @implementation MementoCenter + (void)saveMementoObject:(id <MementoCenterProtocol>)mementoObject withKey:(NSString *)key { NSParameterAssert(mementoObject);
NSParameterAssert(key); NSData *data = [self makeDataWithValue:[mementoObject currentState]]; if (data) { [self storeValue:data with:[self MD5HashWithString:key]];
}
} + (id)mementoObjectWithKey:(NSString *)key { NSParameterAssert(key); NSData *data = [self valueWithKey:[self MD5HashWithString:key]]; if (data) { return [self makeObjectWithData:data]; } else { return nil;
}
} #pragma mark - md5
+ (NSString *)MD5HashWithString:(NSString *)string { CC_MD5_CTX md5; CC_MD5_Init(&md5);
CC_MD5_Update(&md5, [string UTF8String], (CC_LONG) [string length]); unsigned char digest[CC_MD5_DIGEST_LENGTH];
CC_MD5_Final(digest, &md5); NSString *s = [NSString stringWithFormat: @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
digest[], digest[],
digest[], digest[],
digest[], digest[],
digest[], digest[],
digest[], digest[],
digest[], digest[],
digest[], digest[],
digest[], digest[]]; return s;
} #pragma mark - 本地持久化
+ (void)storeValue:(id)value with:(NSString *)key {
[[NSUserDefaults standardUserDefaults] setObject:value forKey:key];
} + (id)valueWithKey:(NSString *)key {
return [[NSUserDefaults standardUserDefaults] objectForKey:key];
} #pragma mark - 使用FastCode来处理对象
+ (NSData *)makeDataWithValue:(id)value {
return [FastCoder dataWithRootObject:value];
} + (id)makeObjectWithData:(NSData *)data {
return [FastCoder objectWithData:data];
} @end
//
// MementoCenterProtocol.h
// MementoPattern
//
// Created by YouXianMing on 15/9/11.
// Copyright (c) 2015年 YouXianMing. All rights reserved.
// #import <Foundation/Foundation.h> @protocol MementoCenterProtocol <NSObject> @required
/**
* 生成当前状态对象值
*
* @return 对象值
*/
- (id)currentState; /**
* 恢复到指定的状态
*
* @param state 状态
*/
- (void)recoverFromState:(id)state; @end
分析
使用FastCoder来作为存储工具