iPhone应用开发之模型对象归档

李程站

iPhone应用开发之模型对象归档是本文要介绍的内容，主要是来介绍归档，它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。来看详细内容。
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];         
  
• }
  

小结：iPhone应用开发之模型对象归档的内容介绍完了，希望通过本文对你有所帮助！
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