return copy;
}

    获取归档文件
  
- (NSString *)dataFilePath {
       NSArray  *paths  =  NSSearchPathForDirectoriesInDomains(  NSDocumentDirectory, 
NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"archive"];
}

    对数据进行归档

FourLines *fourLines = [[FourLines alloc] init];
    fourLines.field1 = field1.text;
    fourLines.field2 = field2.text;
    fourLines.field3 = field3.text;
    fourLines.field4 = field4.text;
   
//对数据进行归档
    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];   

    获取归档数据
  
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;