IPhone之模型对象归档

归档指的是另一种型式的序列化，但它是任保对象都可以实现的更常规的类型。

  其作用为：进行数据的持久化保存。

  对象必须实现NSCodeing协议和NSCopying协议。

@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; }

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;

        field3.text = fourLines.field3;

        field4.text = fourLines.field4;

       

        [unarchiver release];

        [data release];       

    }