歸檔指的是另一種型式的序列化，但它是任保對象都可以實現的更常規的類型。
 
  其作用為：進行數據的持久化保存。
 
  對象必須實現NSCodeing協議和NSCopying協議。
 
@interface FourLines : NSObject <NSCoding, NSCopying> {
    NSString *field1;
    NSString *field2;
    NSString *field3;
    NSString *field4;   
}
@property (nonatomic, retain) NSString *field1;
@property (nonatomic, retain) NSString *field2;
@property (nonatomic, retain) NSString *field3;
@property (nonatomic, retain) NSString *field4;
@end
#pragma mark NSCoding
- (void)encodeWithCoder:(NSCoder *)encoder {
    [encoder encodeObject:field1 forKey:kField1Key];
    [encoder encodeObject:field2 forKey:kField2Key];
    [encoder encodeObject:field3 forKey:kField3Key];
    [encoder encodeObject:field4 forKey:kField4Key];
}
- (id)initWithCoder:(NSCoder *)decoder {
    if (self = [super init]) {
        self.field1 = [decoder decodeObjectForKey:kField1Key];
        self.field2 = [decoder decodeObjectForKey:kField2Key];
        self.field3 = [decoder decodeObjectForKey:kField3Key];
        self.field4 = [decoder decodeObjectForKey:kField4Key];
    }
    return self;
}
#pragma mark NSCopying
- (id)copyWithZone:(NSZone *)zone {
    FourLines *copy = [[[self class] allocWithZone: zone] init];
    copy.field1 = [[self.field1 copyWithZone:zone] autorelease];
    copy.field2 = [[self.field2 copyWithZone:zone] autorelease];
    copy.field3 = [[self.field3 copyWithZone:zone] autorelease];
    copy.field4 = [[self.field4 copyWithZone:zone] autorelease];
   
    return copy;
}
 
 
 
獲取歸檔文件
 
- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"archive"];
}
 
 
對數據進行歸檔
 
FourLines *fourLines = [[FourLines alloc] init];
    fourLines.field1 = field1.text;
    fourLines.field2 = field2.text;
    fourLines.field3 = field3.text;
    fourLines.field4 = field4.text;
   
//對數據進行歸檔
    NSMutableData *data = [[NSMutableData alloc] init];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [archiver encodeObject:fourLines forKey:@"Data"];
    [archiver finishEncoding];
    [data writeToFile:[self dataFilePath] atomically:YES];
    [fourLines release];
    [archiver release];
    [data release];   
 
 
 
獲取歸檔數據
 
    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        NSData *data = [[NSMutableData alloc]
                        initWithContentsOfFile:[self dataFilePath]];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]
                                         initForReadingWithData:data];
        FourLines *fourLines = [unarchiver decodeObjectForKey:@"Data"];
        [unarchiver finishDecoding];
       
        field1.text = fourLines.field1;
        field2.text = fourLines.field2;
        field3.text = fourLines.field3;
        field4.text = fourLines.field4;
       
        [unarchiver release];
        [data release];       
    }