在Cocoa中将自定义对象写入.plist

Question

我阻止某事,我确信它太大了.我有一个看起来像这样的自定义对象

 @interface DownloadObject : NSObject <NSCoding>{
    NSNumber *key; 
    NSString *name; 
    NSNumber *progress; 
    NSNumber *progressBytes; 
    NSNumber *size; 
    NSString *path; 
}
@property (copy) NSNumber *key; 
@property (copy) NSString *name; 
@property (copy) NSNumber *progress; 
@property (copy) NSNumber *size; 
@property (copy) NSString *path; 
@property (copy) NSNumber *progressBytes; 
-(id)initWithKey:(NSNumber *)k name:(NSString *)n progress:(NSNumber *)pro size:(NSNumber *)s path:(NSString *)p progressBytes:(NSNumber *)pb; 
@end

并实施

  @implementation DownloadObject
@synthesize size, progress, name, key, path, progressBytes;

-(id)initWithKey:(NSNumber *)k name:(NSString *)n progress:(NSNumber *)pro size:(NSNumber *)s path:(NSString *)p progressBytes:(NSNumber *)pb  
{
    self.key = k;
    self.name = n; 
    self.progress = pro; 
    self.size = s; 
    self.path = p; 
    self.progressBytes = pb; 

    return self; 
}

-(id) initWithCoder: (NSCoder*) coder {
    if (self = [super init]) {
        self.key = [[coder decodeObjectForKey:@"Key"] retain];
        self.name = [[coder decodeObjectForKey:@"Name"] retain];
        self.progress = [[coder decodeObjectForKey:@"Progress"] retain];
        self.size = [[coder decodeObjectForKey:@"Size"] retain];
        self.path = [[coder decodeObjectForKey:@"Path"] retain];
        self.progressBytes = [[coder decodeObjectForKey:@"ProgressBytes"]retain]; 
    }
    return self;
}


-(void) encodeWithCoder: (NSCoder*) coder {
    [coder encodeObject:self.key forKey:@"Key"]; 
    [coder encodeObject:self.name forKey:@"Name"]; 
    [coder encodeObject:self.progress forKey:@"Progress"]; 
    [coder encodeObject:self.size forKey:@"Size"]; 
    [coder encodeObject:self.path forKey:@"Path"]; 
    [coder encodeObject:self.progressBytes forKey:@"ProgressBytes"]; 
}


-(void)dealloc
{
    [key release]; 
    [name release]; 
    [size release]; 
    [progress release]; 
    [path release]; 
    [progressBytes release]; 
    [super dealloc]; 
}

@end

正如您所看到的,它实现了NSCoding(我认为是这样,NSObject不符合NSCoding).现在,当我尝试做类似的事情只是为了测试

downloadArray = [[[NSMutableArray alloc]init]retain];
NSNumber *number = [NSNumber numberWithInt:10]; 
DownloadObject *object = [[DownloadObject alloc]initWithKey:number name:@"hey" progress:number size:number path:@"hey" progressBytes:number]; 
[downloadArray addObject:object]; 
[object release]; 
[downloadArray writeToFile:path atomically:YES]; 

downloadArray是一个NSMutableArray.我的plist读/写很好,path位于应用程序支持中,当我记录它时显示plist路径.

但它只是没有将数组写入plist,任何想法？

Answer 1

属性列表文件只能存储基本数据类型,不能包含自定义对象.如果要将对象NSData写入plist,则需要将对象转换为对象.您可以使用NSKeyedArchiver,它将符合NSCoding协议的NSData对象编码为对象.

DownloadObject *object = [[DownloadObject alloc]initWithKey:number name:@"hey" progress:number size:number path:@"hey" progressBytes:number];
NSData* objData = [NSKeyedArchiver archivedDataWithRootObject:object];
[downloadArray addObject:objData];
[object release];

如果要从NSData对象重建对象,可以使用NSKeyedUnarchiver:

NSData* objData = [downloadArray objectAtIndex:0];
DownloadObject* object = [NSKeyedUnarchiver unarchiveObjectWithData:objData];

您的代码中也有几个内存泄漏.在您的-initWithCoder:方法中,您不应该使用访问器来设置ivars的值,您应该直接设置ivars,如下所示:

key = [[coder decodeObjectForKey:@"Key"] copy];

您正在调用-retain然后使用指定为的访问器copy,这意味着您的对象的保留计数为2并且不会被释放.通常,您应该避免在init方法中使用访问器.

此外,在您分配downloadArray对象的代码中,您正在调用-alloc然后调用-retain该对象,这将使retainCount为2.您应该重新阅读Objective-C 内存管理指南.

Answer 2

这对我有用：

NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];

[archiver encodeObject:highScoreArray forKey:kHighScoreArrayKey];

[archiver finishEncoding];

[data writeToFile:[self dataFilePath] atomically:YES];

[data release];
[archiver release];