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];
}
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