Model object archiving for iPhone application development

IPhoneModel object for application developmentArchiveIs the content to be introduced in this article, mainly to introduceArchiveIt refers to another type of serialization, but it is a more general type that can be implemented by any object. Its function is to store data persistently. Let's take a look at the details.

The object must implement the NSCodeing protocol and the NSCopying protocol.

 
 

  
  
@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;  
  
  
} 
 
 

Obtain an archive file

 
 

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

Archive data

 
 

  
  
FourLines * fourLines = [[FourLines alloc] init];
  
  
FourLines. field1 = field1.text;
  
  
FourLines. field2 = field2.text;
  
  
FourLines. field3 = field3.text;
  
  
FourLines. field4 = field4.text;
  
  
// Archive data
  
  
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];
 
 

Obtain archive data

 
 

  
  
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];         
  
  
} 
 
 

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