struct objc_class {
 Class isa;//指针，顾名思义，表示是一个什么，
 //实例的isa指向类对象，类对象的isa指向元类

#if !__OBJC2__
 Class super_class; //指向父类
 const char *name; //类名
 long version;
 long info;
 long instance_size
 struct objc_ivar_list *ivars //成员变量列表
 struct objc_method_list **methodLists; //方法列表
 struct objc_cache *cache;//缓存
 //一种优化，调用过的方法存入缓存列表，下次调用先找缓存
 struct objc_protocol_list *protocols //协议列表
 #endif
} OBJC2_UNAVAILABLE;
/* Use `Class` instead of `struct objc_class *` */

#import <objc/runtime.h>

// 输出类的一些信息
- (void)logInfo {
 unsigned int count;// 用于记录列表内的数量，进行循环输出

 // 获取属性列表
 objc_property_t *propertyList = class_copyPropertyList([self class], &count);
 for (unsigned int i = 0; i < count; i++) {
 const char *propertyName = property_getName(propertyList[i]);
 NSLog(@"property --> %@", [NSString stringWithUTF8String:propertyName]);
 }

 // 获取方法列表
 Method *methodList = class_copyMethodList([self class], &count);
 for (unsigned int i; i < count; i++) {
 Method method = methodList[i];
 NSLog(@"method --> %@", NSStringFromSelector(method_getName(method)));
 }

 // 获取成员变量列表
 Ivar *ivarList = class_copyIvarList([self class], &count);
 for (unsigned int i; i < count; i++) {
 Ivar myIvar = ivarList[i];
 const char *ivarName = ivar_getName(myIvar);
 NSLog(@"Ivar --> %@", [NSString stringWithUTF8String:ivarName]);
 }

 // 获取协议列表
 __unsafe_unretained Protocol **protocolList = class_copyProtocolList([self class], &count);
 for (unsigned int i; i < count; i++) {
 Protocol *myProtocal = protocolList[i];
 const char *protocolName = protocol_getName(myProtocal);
 NSLog(@"protocol --> %@", [NSString stringWithUTF8String:protocolName]);
 }
}

// 调用不存在的类方法时触发，默认返回NO，可以加上自己的处理后返回YES
+ (BOOL)resolveClassMethod:(SEL)sel;

// 调用不存在的实例方法时触发，默认返回NO，可以加上自己的处理后返回YES
+ (BOOL)resolveInstanceMethod:(SEL)sel;

// 将调用的不存在的方法重定向到一个其他声明了这个方法的类里去，返回那个类的target
- (id)forwardingTargetForSelector:(SEL)aSelector;

// 将调用的不存在的方法打包成 NSInvocation 给你，自己处理后调用 invokeWithTarget: 方法让某个类来触发
- (void)forwardInvocation:(NSInvocation *)anInvocation;

@interface ViewController ()
@property (nonatomic, strong) UIButton *logBtn;

- (void)notHas;// 要调用的实例方法，没有具体实现
@end

- (void)viewDidLoad {
 [super viewDidLoad];

 // 添加按钮
 self.logBtn = [[UIButton alloc] initWithFrame:CGRectMake(100, 200, 100, 20)];
 [self.logBtn setTitle:@"测 试" forState:UIControlStateNormal];
 [self.logBtn setTitleColor:[UIColor lightGrayColor] forState:UIControlStateNormal];
 // 添加没有实现的点击事件
 [self.logBtn addTarget:self action:@selector(notHas) forControlEvents:UIControlEventTouchUpInside];
 [self.view addSubview:self.logBtn];

}

// 拦截对不存在的方法的调用
+ (BOOL)resolveInstanceMethod:(SEL)sel {
 NSLog(@"notFind!");
 // 给本类动态添加一个方法
 if ([NSStringFromSelector(sel) isEqualToString:@"notHas"]) {
 class_addMethod(self, sel, (IMP)runAddMethod, "v@:*");
 }
 // 注意要返回YES
 return YES;
}

// 要动态添加的方法，这是一个C方法
 void runAddMethod(id self, SEL _cmd, NSString *string) {
 NSLog(@"动态添加一个方法来提示");
}

 // 关联对象
 static char associatedObjectKey;
 objc_setAssociatedObject(self, &associatedObjectKey, @"我就是要关联的字符串对象内容", OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 NSString *theString = objc_getAssociatedObject(self, &associatedObjectKey);
 NSLog(@"关联对象：%@", theString);

enum {
 OBJC_ASSOCIATION_ASSIGN = 0,
 OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1, 
 OBJC_ASSOCIATION_COPY_NONATOMIC = 3,
 OBJC_ASSOCIATION_RETAIN = 01401,
 OBJC_ASSOCIATION_COPY = 01403 
};

//添加关联对象
- (void)addAssociatedObject:(id)object{
 objc_setAssociatedObject(self, @selector(getAssociatedObject), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

//获取关联对象
- (id)getAssociatedObject{
 return objc_getAssociatedObject(self, _cmd);
}