数据持久化之NSKeyedArchiver

   基本的数据类型如NSString、NSDictionary、NSArray、NSData、NSNumber等可以用属性列表的方法持久化到.plist 文件中，但如果是一些自定义的类的话，属性列表的方法就不管用了。archiver 方法可以做到。

编码如下：

     首先新建一个person类，定义它的三个属性，如下：

//
//  person.h
//  数据持久化之archiver
//
//  Created by Rio.King on 13-9-22.
//  Copyright (c) 2013年 Rio.King. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface person : UIView<NSCoding>
@property(nonatomic, assign) int age;
@property(nonatomic, copy)NSString *name;
@property(nonatomic, assign)float height;
@end

//
//  person.m
//  数据持久化之archiver
//
//  Created by Rio.King on 13-9-22.
//  Copyright (c) 2013年 Rio.King. All rights reserved.
//

#import "person.h"

@implementation person


#pragma mark 写入文件
-(void)encodeWithCoder:(NSCoder *)encoder{
    [super encodeWithCoder:encoder];//不要忘了这个
    [encoder encodeInt:self.age forKey:@"age"];
    [encoder encodeObject:self.name forKey:@"name"];
    [encoder encodeFloat:self.height forKey:@"height"];
}

#pragma mark 从文件中读取
-(id)initWithCoder:(NSCoder *)decoder{
    self = [super initWithCoder:decoder];//不要忘了这个
    self.age = [decoder decodeIntForKey:@"age"];
    self.name = [decoder decodeObjectForKey:@"name"];
    self.height = [decoder decodeFloatForKey:@"height"];
    
    
    return self;
}


-(NSString *)description{
    return [NSString stringWithFormat:@"name = %@, age = %d, height = %f",self.name,self.age,self.height];
}

//释放资源
-(void)dealloc{
    [super dealloc];
    [_name release];
}
@end

然后再ViewController.m文件中写如下代码：

//
//  ViewController.m
//  数据持久化之archiver
//
//  Created by Rio.King on 13-9-22.
//  Copyright (c) 2013年 Rio.King. All rights reserved.
//

#import "ViewController.h"
#import "person.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self createPerson];
    [self readPerson];
}

//创建
-(void)createPerson{
    
    person *p = [[[person alloc] init] autorelease];
    p.age = 20;
    p.name = @"Rio";
    p.height =1.75f;
    
    //获得Document的路径
    NSString *documents = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [documents stringByAppendingPathComponent:@"person.archiver"];//拓展名可以自己随便取
    
    [NSKeyedArchiver archiveRootObject:p toFile:path];
    
}

//读取
-(void)readPerson{
    NSString *documents = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [documents stringByAppendingPathComponent:@"person.archiver"];
    person *person1 = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"%@",person1);
}

@end

在写ViewController.m文件代码的时候，必须在头文件中遵循NSCoding协议。

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<NSCoding>

@end

 

运行结果如下:

 

 

2013-09-22 13:31:39.509 数据持久化之archiver[1080:c07] name = Rio, age = 20, height = 1.750000

 

注意事项：

 

1.遵循NSCoding协议

NSCoding协议声明了两个方法，这两个方法都是必须实现的。一个用来说明如何将对象编码到归档中，另一个说明如何进行解档来获取一个新对象。

• 遵循协议和设置属性

    //1.遵循NSCoding协议 
    @interface Person : NSObject <NSCoding>
  
    //2.设置属性
    @property (strong, nonatomic) UIImage *avatar;
    @property (copy, nonatomic) NSString *name;
    @property (assign, nonatomic) NSInteger age;
  
    @end

   

• 实现协议方法

   //解档
    - (id)initWithCoder:(NSCoder *)aDecoder {
        if ([super init]) {
            self.avatar = [aDecoder decodeObjectForKey:@"avatar"];
            self.name = [aDecoder decodeObjectForKey:@"name"];
            self.age = [aDecoder decodeIntegerForKey:@"age"];
        }
  
        return self;
    }
  
    //归档
    - (void)encodeWithCoder:(NSCoder *)aCoder {
        [aCoder encodeObject:self.avatar forKey:@"avatar"];
        [aCoder encodeObject:self.name forKey:@"name"];
        [aCoder encodeInteger:self.age forKey:@"age"];
    }

   

2.使用

• 需要把对象归档是调用NSKeyedArchiver的工厂方法 archiveRootObject: toFile: 方法。

   NSString *file = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject stringByAppendingPathComponent:@"person.data"];
  
    Person *person = [[Person alloc] init];
    person.avatar = self.avatarView.image;
    person.name = self.nameField.text;
    person.age = [self.ageField.text integerValue];
  
    [NSKeyedArchiver archiveRootObject:person toFile:file];

   

• 需要从文件中解档对象就调用NSKeyedUnarchiver的一个工厂方法 unarchiveObjectWithFile: 即可。

   NSString *file = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject stringByAppendingPathComponent:@"person.data"];
    Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:file];
    if (person) {
       self.avatarView.image = person.avatar;
       self.nameField.text = person.name;
       self.ageField.text = [NSString stringWithFormat:@"%ld", person.age];
    }

   

3.注意

• 必须遵循并实现NSCoding协议
• 保存文件的扩展名可以任意指定
• 继承时必须先调用父类的归档解档方
• 如果需要归档的类是某个自定义类的子类时，就需要在归档和解档之前先实现父类的归档和解档方法。即 [super encodeWithCoder:aCoder] 和 [super initWithCoder:aDecoder]方法;

 

如果要归档Book类的子类对象，那么要在encodeWithCoder和decodeWithCoder方法中首先调用父类的编码和解码方法。这里要注意，如果在Book类中<NSCoding>协议声明在匿名类别中，那么协议的方法将是私有的，子类无法访问，因此要将<NSCoding>协议声明移到接口部分：

@interface Book () // <NSCoding>
@end

 

修改为： 

@interface Book : NSObject <NSCoding>

 

下面新建一个Book类的子类Literature类：

#import "Book.h"

@interface Literature : Book <NSCoding>

@property (copy, nonatomic) NSString *author;

@end
#import "Literature.h"

static NSString *kAuthor = @"LiteratureAuthor";

@implementation Literature

- (NSString *)description {
    NSString *bookDes  = [super description];
    NSString *literDes = [bookDes stringByAppendingFormat:@"Author = %@", self.author];
    return literDes;
}

#pragma mark - NSCoding

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [super encodeWithCoder:aCoder];
    [aCoder encodeObject:self.author forKey:kAuthor];
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    self.author = [aDecoder decodeObjectForKey:kAuthor];
    return self;
}

@end

 

在archive的action方法中加入Literature类对象，并进行归档：

// 创建Book子类对象
    Literature *literature = [[Literature alloc] init];
    literature.author = @"Shakespeare";
    literature.name = book.name;
    literature.published = book.published;
    literature.price = book.price;
    literature.info = [[NSMutableArray alloc] initWithArray:[book.info copy]];
    
    NSArray *array = [NSArray arrayWithObjects:str, date, number, book, literature, nil];

 

运行结果：