给系统类扩展属性(枚举)或方法

@interface UIButton (CJButtonType)
@property (nonatomic, strong) NSString *typeString;
@end
///////////////////////////////////////////////
#import "UIButton+CJButtonType.h"
#import <objc/runtime.h>
@implementation UIButton (CJButtonType)
- (NSString *)typeString {
    return objc_getAssociatedObject(self, @selector(typeString));
}
- (void)setTypeString:(NSString *)typeString {
    objc_setAssociatedObject(self, @selector(typeString), typeString, OBJC_ASSOCIATION_RETAIN_NONATOMIC);   
}
@end

#import <UIKit/UIKit.h>
typedef NS_ENUM(NSUInteger, BuyHouseCalculatorType) {
    BuyHouseCalculatorType_PublicReserveFundLoan = 0, 
    BuyHouseCalculatorType_BusinessLoan,              
    BuyHouseCalculatorType_GroupLoan                  
};
@interface UIButton (CJButtonType)
@property (nonatomic, assign) BuyHouseCalculatorType buyHouseCalculatorType;
@end

#import "UIButton+CJButtonType.h"
#import <objc/runtime.h>
// 定义全局静态字符作为关联的Key值
const char *buyHouseCalculatorTypeKey = "buyHouseCalculatorTypeKey";
@implementation UIButton (CJButtonType)
- (void)setBuyHouseCalculatorType:(BuyHouseCalculatorType)buyHouseCalculatorType {
    objc_setAssociatedObject(self, buyHouseCalculatorTypeKey, @(buyHouseCalculatorType), OBJC_ASSOCIATION_ASSIGN);
}
- (BuyHouseCalculatorType)buyHouseCalculatorType {
    return [objc_getAssociatedObject(self, buyHouseCalculatorTypeKey) integerValue];
    
}
@end

//// .h
+ (UIButton *)button;
+ (UIButton *)buttonWithTitle:(NSString *)title titleColor:(UIColor *)color;
////  .m
+ (UIButton *)button {
    UIButton *button = [[UIButton alloc] initWithFrame:CGRectZero];
    [button setClipsToBounds:YES];
    [button setExclusiveTouch:YES];
    return button;
}
+ (UIButton *)buttonWithTitle:(NSString *)title titleColor:(UIColor *)color {
    UIButton *button = [UIButton button];
    [button setTitle:title forState:UIControlStateNormal];
    [button setTitleColor:color forState:UIControlStateNormal];
    return button;
}