如何在类别中添加属性

@interface NSObject (AssociatedObject)
@property (nonatomic, strong) id associatedObject;
@end

@implementation NSObject (AssociatedObject)
@dynamic associatedObject;

- (void)setAssociatedObject:(id)object {
objc_setAssociatedObject(self, @selector(associatedObject), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)associatedObject {
return objc_getAssociatedObject(self, @selector(associatedObject));
}

@interface UIView (DHStyleManager)

@property (nonatomic, copy) NSString* styleName;

@end

#import "UIViewDHStyleManager.h"

NSString * const kDHStyleKey = @"kDHStyleKey";

@implementation UIView (DHStyleManager)

- (void)setStyleName:(NSString *)styleName

{

objc_setAssociatedObject(self, kDHStyleKey, styleName, OBJC_ASSOCIATION_COPY);

}

- (NSString*)styleName

{

return objc_getAssociatedObject(self, kDHStyleKey);

}

@end

static char kDHStyleKey;

@interface UIView (DHStyleManager)

@property (nonatomic, copy) NSString* styleName;

@end
@implementation UIView (DHStyleManager)

@dynamic styleName;

- (void)setStyleName:(NSString *)styleName

{

objc_setAssociatedObject(self, &kDHStyleKey, styleName, OBJC_ASSOCIATION_COPY);

}

- (NSString*)styleName

{

return objc_getAssociatedObject(self, &kDHStyleKey);

}

@end