IOS之数据持久化二（归档与反归档）

   数据持久化，实际上就是将数据存放到网络或者硬盘上，这里是存储到本地的硬盘上，应用程序的本地硬盘是沙盒，沙盒实际上就是一个文件夹，它下面有4个文件夹。分别是Documents，Library，APP包和tmp文件夹，Documents里面主要是存储用户长期使用的文件，Library里面又有Caches和Preferences文件夹，Caches里面存放的是临时的文件，缓存。Preferences里面存放的是偏好设置。tmp里面也是临时的文件，不过和Caches还有区别，APP包里面是编译后的一些文件，包不能修改。

先创建一个Person类，定义3个属性

.h文件

#import<Foundation/Foundation.h>

@interface Person :NSObject<NSCoding>

{

    NSString *name;

    int age;

    NSString *phone;

}

@property(nonatomic,retain)NSString *name, *phone;

@property(nonatomic,assign)int age;

-(id)initWithName:(NSString *)aName phone:(NSString *)aPhone age:(int)aAge;//初始化方法

@end

.m文件

#import"Person.h"

@implementation Person

@synthesize name,age,phone;

-(id)initWithName:(NSString *)aName phone:(NSString *)aPhone age:(int)aAge

{

    [superinit];

    if (self) {

        self.name = aName;

        self.phone = aPhone;

        self.age = aAge;

    }

   return self;

    

}

- (void)encodeWithCoder:(NSCoder *)aCoder //将属性进行编码

{

    [aCoder encodeObject:self.nameforKey:@"name"];

    [aCoder encodeObject:self.phoneforKey:@"phone"];

    [aCoderencodeInteger:self.ageforKey:@"age"];

    

}

- (id)initWithCoder:(NSCoder *)aDecoder //将属性进行解码

{

    NSString *name1 = [aDecoder decodeObjectForKey:@"name"];

    NSString *phone1 = [aDecoder decodeObjectForKey:@"phone"];

    int age1 = [aDecoder decodeIntegerForKey:@"age"];

    

    [selfinitWithName:name1 phone:phone1 age:age1];    

    

   return self;

    

    

    

}

@end

主程序中进行归档与反归档

- (void)loadView

{

    self.view = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 460)];

    self.view.backgroundColor = [UIColor whiteColor];

    

    Person *p1 = [[Person alloc]initWithName:@"jim" phone:@"654789" age:3];

    Person *p2 = [[Person alloc]initWithName:@"tom" phone:@"5464" age:4];

    //文件的归档

    NSMutableData *data = [NSMutableData data ];

    //创建一个归档类

    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]initForWritingWithMutableData:data];

    [archiver encodeObject:p1 forKey:@"Person1"];

    [archiver encodeObject:p2 forKey:@"Person2"];

    [archiver finishEncoding];

    [archiver release];

    //将数据写入文件里

    [data writeToFile:[self filePath] atomically:YES];

    //反归档，从文件中取出数据

    NSMutableData *data1 = [NSMutableData dataWithContentsOfFile:[self filePath]];

    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]initForReadingWithData:data1];

    Person *p3  = [unarchiver decodeObjectForKey:@"Person1"];

    Person *p4 =  [unarchiver decodeObjectForKey:@"Person2"];

    NSLog(@"%@ %@ %d",p3.name,p3.phone,p3.age);

    NSLog(@"%@ %@ %d",p4.name,p4.phone,p4.age);

}

-(NSString *)filePath

{

    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDirectory, YES)objectAtIndex:0];

    NSString *path = [docPath stringByAppendingPathComponent:@"texts"];

 //  NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches/texts"]; //两种方法都可以

    

    return path;

}