设计模式 - 备忘录

备忘录模式很简单，就是存储对象，然后支持恢复对象到之前的某个状态，玩过游戏的，一定懂得存档一说，备忘录就是对对象的存档与管理。

效果：

这个需要配合FastCoder使用，请自行到Github上去搜索源码FastCoder源码^_^!

源码：

Model.h 与 Model.m

//
//  Model.h
//  MementoPattern
//
//  Created by YouXianMing on 15/1/3.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Model : NSObject

@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSString *age;

/**
 *  初始化方法
 *
 *  @param key 用来标示对象唯一性
 *
 *  @return 对象
 */
- (instancetype)initWithKey:(NSString *)key;

/**
 *  从某个状态恢复
 *
 *  @param slot 状态槽位（第几个存档位置）
 *  @param key  标示字符串（保证存档唯一）
 *
 *  @return 存档的对象，如果对象不存在，则重新创建
 */
+ (id)recoverFromSlot:(NSInteger)slot key:(NSString *)key;

/**
 *  存储到slot当中（按照数组的顺序）
 */
- (void)store;

@end

//
//  Model.m
//  MementoPattern
//
//  Created by YouXianMing on 15/1/3.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import "Model.h"
#import "FastCoder.h"
#import "NSString+File.h"

@interface Model ()

@property (nonatomic, strong) NSString        *key;
@property (nonatomic, strong) NSMutableArray  *slotInfoArray;

@end

@implementation Model

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.key = @"Default";
    }
    return self;
}

- (instancetype)initWithKey:(NSString *)key {
    Model *model = [Model new];
    model.key    = key;

    return model;
}

+ (id)recoverFromSlot:(NSInteger)slot key:(NSString *)key {

    if (key == nil) {
        key = @"Default";
    }

    NSString *arrayPath  =  [[@"/Documents" path] stringByAppendingString:[NSString stringWithFormat:@"/%@_array", key]];
    NSString *objectPath =  [[@"/Documents" path] stringByAppendingString:[NSString stringWithFormat:@"/%@_%ld", key, (long)slot]];

    id object = nil;

    NSArray *array = [FastCoder objectWithData:[self dataWithPath:arrayPath]];
    if (array.count > slot && slot >= 0) {
        object = [FastCoder objectWithData:[self dataWithPath:objectPath]];
    }

    return object;
}

- (void)store {
    if (self == nil) {
        return;
    }

    self.slotInfoArray = [FastCoder objectWithData:[self dataWithPath:[self arrayPath]]];
    if (self.slotInfoArray.count == 0) {
        [[FastCoder dataWithRootObject:self] writeToFile:[self filePathAtSlot:0]
                                              atomically:YES];

        self.slotInfoArray = [NSMutableArray array];
        [self.slotInfoArray addObject:@""];
        [[FastCoder dataWithRootObject:self.slotInfoArray] writeToFile:[self arrayPath]
                                                            atomically:YES];
    } else {
        [[FastCoder dataWithRootObject:self] writeToFile:[self filePathAtSlot:self.slotInfoArray.count]
                                              atomically:YES];

        [self.slotInfoArray addObject:@""];
        [[FastCoder dataWithRootObject:self.slotInfoArray] writeToFile:[self arrayPath]
                                                            atomically:YES];
    }

    NSLog(@"store sucess!");
}

#pragma mark - private method
- (NSString *)filePathAtSlot:(NSInteger)slot {
    NSString *path =  [[@"/Documents" path] stringByAppendingString:[NSString stringWithFormat:@"/%@_%ld", self.key, (long)slot]];

    return path;
}
- (NSString *)arrayPath {
    NSString *path =  [[@"/Documents" path] stringByAppendingString:[NSString stringWithFormat:@"/%@_array", self.key]];

    return path;
}
- (NSData *)dataWithPath:(NSString *)path {
    return [NSData dataWithContentsOfFile:path];
}
+ (NSData *)dataWithPath:(NSString *)path {
    return [NSData dataWithContentsOfFile:path];
}

@end

NSString+File.h 与 NSString+File.m

//
//  NSString+File.h
//  Category
//
//  Created by YouXianMing on 14-8-29.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (File)

// 沙盒路径
- (NSString *)path;
/*
 /Documents
 /Library/Caches
 /Library/Preferences
 /tmp
 */

// bundle文件
- (NSString *)bundleFile;

// 检测文件或者文件夹是否存在
- (BOOL)exist;

// 创建文件夹
- (BOOL)createFolder;

// 是否是文件夹
- (BOOL)isDirectory;

// 复制到这个路径
- (BOOL)copyTo:(NSString *)path;

// 移动到这个路径
- (BOOL)moveTo:(NSString *)path;

// 删除文件
- (BOOL)remove;

// 遍历出文件夹中的文件
- (NSArray *)enumeratorFolder;

// 遍历出文件夹并在block中查看
- (void)enumeratorFolderEach:(void (^)(NSString *path))block;

// 文件信息
- (NSDictionary *)fileInfo;

// 文件大小
- (int)fileSize;

@end

//
//  NSString+File.m
//  Category
//
//  Created by YouXianMing on 14-8-29.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import "NSString+File.h"

@implementation NSString (File)

- (NSString *)path
{
    return [NSHomeDirectory() stringByAppendingPathComponent:self];
}

- (NSString *)bundleFile
{
    return [[NSBundle mainBundle] pathForResource:self
                                           ofType:nil];
}

- (BOOL)exist
{
    return [[NSFileManager defaultManager] fileExistsAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                isDirectory:NO];
}

- (BOOL)createFolder
{
    return [[NSFileManager defaultManager] createDirectoryAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                     withIntermediateDirectories:YES
                                                      attributes:nil
                                                           error:nil];
}

- (BOOL)isDirectory
{
    BOOL isDirectory = NO;

    [[NSFileManager defaultManager] fileExistsAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                         isDirectory:&isDirectory];

    return isDirectory;
}

- (BOOL)copyTo:(NSString *)path
{
    return [[NSFileManager defaultManager] copyItemAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                   toPath:[NSHomeDirectory() stringByAppendingPathComponent:path]
                                                    error:nil];
}

- (BOOL)moveTo:(NSString *)path
{
    return [[NSFileManager defaultManager] moveItemAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                   toPath:[NSHomeDirectory() stringByAppendingPathComponent:path]
                                                    error:nil];
}

- (BOOL)remove
{
    return [[NSFileManager defaultManager] removeItemAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                      error:nil];
}

- (NSArray *)enumeratorFolder
{
    if ([self isDirectory])
    {
        NSMutableArray *storeArray = [NSMutableArray array];

        NSString *docsDir = [NSHomeDirectory() stringByAppendingPathComponent:self];
        NSFileManager *localFileManager = [[NSFileManager alloc] init];
        NSDirectoryEnumerator *dirEnum = [localFileManager enumeratorAtPath:docsDir];

        NSString *file;
        while ((file = [dirEnum nextObject]))
        {
            [storeArray addObject:[[NSHomeDirectory() stringByAppendingPathComponent:self] stringByAppendingPathComponent:file]];
        }

        return storeArray;
    }
    else
    {
        return nil;
    }
}

- (void)enumeratorFolderEach:(void (^)(NSString *path))block
{
    if ([self isDirectory])
    {
        NSMutableArray *storeArray = [NSMutableArray array];

        NSString *docsDir = [NSHomeDirectory() stringByAppendingPathComponent:self];
        NSFileManager *localFileManager = [[NSFileManager alloc] init];
        NSDirectoryEnumerator *dirEnum = [localFileManager enumeratorAtPath:docsDir];

        NSString *file;
        while ((file = [dirEnum nextObject]))
        {
            [storeArray addObject:[self stringByAppendingPathComponent:file]];
        }

        [storeArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            block(obj);
        }];
    }
}

- (NSDictionary *)fileInfo
{
    return [[NSFileManager defaultManager] attributesOfItemAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                            error:nil];
}

- (int)fileSize
{
    return [[[[NSFileManager defaultManager] attributesOfItemAtPath:[NSHomeDirectory() stringByAppendingPathComponent:self]
                                                              error:nil]              objectForKey:@"NSFileSize"] intValue];
}

@end

控制器源码：

//
//  ViewController.m
//  MementoPattern
//
//  Created by YouXianMing on 15/1/3.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import "ViewController.h"
#import "NSString+File.h"
#import "Model.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    Model *model_01 = [Model new];
    model_01.name   = @"YouXianMing";
    model_01.age    = @"27";
    [model_01 store]; // 存快照

    Model *model_02 = [Model new];
    model_02.name   = @"QiuLiang";
    model_02.age    = @"28";
    [model_02 store]; // 存快照

    Model *model_03 = [Model new];
    model_03.name   = @"XiaoMing";
    model_03.age    = @"100";
    [model_03 store]; // 存快照

//    Model *test_model_01 = [Model recoverFromSlot:0 key:nil];
//    NSLog(@"%@ %@", test_model_01.name, test_model_01.age);
//
//    Model *test_model_02 = [Model recoverFromSlot:1 key:nil];
//    NSLog(@"%@ %@", test_model_02.name, test_model_02.age);
//
//    Model *test_model_03 = [Model recoverFromSlot:2 key:nil];
//    NSLog(@"%@ %@", test_model_03.name, test_model_03.age);
}

@end

几个关键的地方：

原理其实非常简单，就是将对象写文件，然后从文件从恢复出对象，但一定要有管理的功能，本例中并没有处理如何删除存档，其实存档可以做成堆栈或者队列模式，这个因需求而已，本处本人只是抛砖引玉，简单介绍下备忘录设计模式！