objective-c - NSInteger 和 decodeInteger :forKey: Problems

Question

我有以下两种归档方式:

    - (void) encodeWithCoder: (NSCoder *) encoder {
    [encoder encodeObject:self.exercises forKey:@"exercises"];
    [encoder encodeObject:self.title forKey:@"title"];
    [encoder encodeObject:self.description forKey:@"description"];
    [encoder encodeInteger:self.idnum forKey:@"idnum"];
    [encoder encodeInteger:self.rating forKey:@"rating"];
    [encoder encodeInteger:self.frequency forKey:@"frequency"];
    NSLog(@"Encoding!");

}

- (id) initWithCoder: (NSCoder *) decoder {
    self.exercises =   [[decoder decodeObjectForKey:@"exercises"] retain];
    self.title =       [[decoder decodeObjectForKey:@"title"] retain];
    self.description = [[decoder decodeObjectForKey:@"description"] retain];
    self.idnum =       [[decoder decodeIntegerForKey:@"idnum"] retain];
    self.rating =      [[decoder decodeIntegerForKey:@"rating"] retain];
    self.frequency =   [[decoder decodeIntegerForKey:@"frequency"] retain];
    NSLog(@"Decoding!");
    return self;
}

还有一个标题:

    @interface Workout : NSObject{

    NSMutableArray *exercises; 
    NSString *title;
    NSString *description;
    NSInteger idnum;
    NSInteger rating;
    NSInteger frequency;
}

- (void) encodeWithCoder: (NSCoder *) encoder;
- (id) initWithCoder: (NSCoder *) decoder;

@property(nonatomic,retain) NSMutableArray *exercises; 
@property(nonatomic,retain) NSString *title;
@property(nonatomic,retain) NSString *description;
@property(nonatomic) NSInteger idnum;
@property(nonatomic) NSInteger rating;
@property(nonatomic) NSInteger frequency;
@end

看起来很简单。 encodeInteger 接受一个 NSInteger，我将其传递给它，decodeIntegerForKey 返回一个 NSInteger，但我得到了这个奇怪的错误:

警告:无效的接收者类型“NSInteger”

当执行 decodeIntegerForKey 指令时，我得到一个 exec bad access。

为什么会这样？

Answer 1

发布的代码有几个问题。第一:

self.idnum =       [[decoder decodeIntegerForKey:@"idnum"] retain];

该代码正在将“保留”发送到 NSInteger。 NSIntegers 不是对象，它们只是标量。那是非法的。只需使用它:

self.idnum =       [decoder decodeIntegerForKey:@"idnum"];

接下来，这段代码:

self.exercises =   [[decoder decodeObjectForKey:@"exercises"] retain];

保留过多，会造成泄漏。由于您声明了如下练习:

@property(nonatomic,retain) NSMutableArray *exercises; 

“保留”意味着当您调用 setter 时，它将保留传入的值，然后再将其粘贴到“练习”实例变量中。不过，您在调用 setter 之前保留，所以这是双重保留。

您可以通过将代码更改为以下之一来解决此问题:

exercises =   [[decoder decodeObjectForKey:@"exercises"] retain];

或者:

self.exercises =   [decoder decodeObjectForKey:@"exercises"];