在分类中添加属性，使用对象关联来实现：
例子：创建一个label的分类
#import
@interfaceUILabel (FontAndColor)
@property (nonatomic, copy) NSString *name;//分类中创建了一个name属性
-(void)WithFont:(int)font withColor:(UIColor*)color withTextAlig:(NSTextAlignment)texAli;
@end
#import "UILabel+FontAndColor.h"
#import
@implementationUILabel (FontAndColor)
static NSString *key = @"associatedObject";
-(void)WithFont:(int)font withColor:(UIColor*)color withTextAlig:(NSTextAlignment)texAli{
self.font = [UIFont systemFontOfSize:font];
self.textColor= color;
self.textAlignment= texAli;
}
-(void)setName:(NSString*)name{//关联实现
objc_setAssociatedObject(self, @selector(name), name, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
-(NSString*)name{//获取值
return objc_getAssociatedObject(self, _cmd);
}
@end
