分类添加属性

objective-c

#import <UIKit/UIKit.h>
@interface UILabel (Name)
@property (nonatomic, strong) NSString * name;
@end

#import "UILabel+Name.h"
#import <objc/runtime.h>
@implementation UILabel (Name)
static char *nameKey = "name";

- (NSString *)name {
    return objc_getAssociatedObject(self, nameKey);
}
- (void)setName:(NSString *)name {
    objc_setAssociatedObject(self, nameKey, name, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
@end

swift

privatevar key:Int = 0
extension FofTrendResp {
    var pointState:NSMutableArray {
        get {
           return (objc_getAssociatedObject(self, &key) as? NSMutableArray)!
        }
        set(newValue) {
           objc_setAssociatedObject(self, &key, newValue, objc_AssociationPolicy(rawValue: objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN.rawValue)!)
        }
    }
}