IOS之資料持久化二（歸檔與反歸檔）

   資料持久化，實際上就是將資料存放到網路或者硬碟上，這裡是儲存到本地的硬碟上，應用程式的本地硬碟是沙箱，沙箱實際上就是一個檔案夾，它下面有4個檔案夾。分別是Documents，Library，APP包和tmp檔案夾，Documents裡面主要是儲存使用者長期使用的檔案，Library裡面又有Caches和Preferences檔案夾，Caches裡面存放的是臨時的檔案，緩衝。Preferences裡面存放的是喜好設定。tmp裡面也是臨時的檔案，不過和Caches還有區別，APP包裡面是編譯後的一些檔案，包不能修改。

先建立一個Person類，定義3個屬性

.h檔案

#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檔案

#import
"Person.h"

@implementation Person

@synthesize name,age,phone;

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

{

    [super
init];

   
if (self) {

       
self.name = aName;

       
self.phone = aPhone;

       
self.age = aAge;

    }

   
return self;

    

}

- (void)encodeWithCoder:(NSCoder *)aCoder //將屬性進行編碼

{

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

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

    [aCoder
encodeInteger:self.age
forKey:@"age"];

    

}

- (id)initWithCoder:(NSCoder *)aDecoder //將屬性進行解碼

{

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

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

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

    

    [self
initWithName:name1
phone:phone1 age:age1];    

    

   
return self;

    

    

    

}

@end

主程式中進行歸檔與反歸檔

- (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];

    //檔案的歸檔

    NSMutableData *data = [NSMutableData data ];

    //建立一個歸檔類

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

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

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

    [archiver finishEncoding];

    [archiver release];

    //將資料寫入檔案裡

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

    //反歸檔，從檔案中取出資料

    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"]; //兩種方法都可以

    

    return path;

}