成员变量 | 类相关

   person *perso = [[person alloc]init];
    
        //获取元类or类
        NSLog(@"%p---%p", object_getClass([person class]),[perso class]);
        
        //设置isa指向的class
        object_setClass(perso,[cat class]);
        [perso performSelectorOnMainThread:@selector(run) withObject:nil waitUntilDone:YES];
        
        //生成对象 添加成员 添加方法 赋值成员
        Class newClass = objc_allocateClassPair([NSObject class], "Dog", 0);
        
        //方法任何时候可以添加
        class_addMethod(newClass, @selector(run), (IMP)run, "v@:");
        //在注册之前 已存在的不能添加
        class_addIvar(newClass, "_age2", 4, 1, @encode(int));
        
        //注册类
        objc_registerClassPair(newClass);
        
        id dyClass = [newClass new];
        [dyClass setValue:@20 forKey:@"_age2"];
        //不需要使用的时候 释放
//        objc_disposeClassPair(newClass);
        
        
        //获取成员变量
        person *perso2 = [[person alloc]init];
        Ivar nameIvar = class_getInstanceVariable([perso2 class], "_name");
        Ivar ageIvar = class_getInstanceVariable([perso2 class], "_age");
        NSLog(@"%s--- %s",ivar_getName(ageIvar),ivar_getTypeEncoding(ageIvar));
        
        //设置和获取成员变量的值 最后一个参数非空对象
        object_setIvar(perso2, nameIvar, @"12345");
        object_setIvar(perso2, ageIvar, (__bridge id _Nullable)((void *)10));
        NSLog(@"----%@---%d",perso2.name,perso2.age);
        
        //成员变量的数量
        unsigned int cout;
        Ivar *ivars = class_copyIvarList([perso2 class], &cout);
        
        /*
         1, 这里我们可以拿到某些控件的私有属性,来进行一些操作
         如利用kvc ,给textfield的placehold属性进行赋值.
         
         2, 字典转模型
         */
        for (int i = 0; i < cout; i++) {
            Ivar ivar = ivars[i];
            NSLog(@"%s",ivar_getName(ivar));
        }
        

方法相关

void running(id self,SEL _cmd){
    NSLog(@"running");
}

        
        cat *c1 = [[cat alloc]init];
//        class_replaceMethod([c1 class], @selector(run), (IMP)run2, "v@:");
        //方法替换
        class_replaceMethod([c1 class], @selector(run), imp_implementationWithBlock(^{
            NSLog(@"block");
            
        }), "v");
        [c1 run];
        
        Method thod1 = class_getInstanceMethod([c1 class], @selector(run));
        Method thod2 = class_getInstanceMethod([c1 class], @selector(otherRun));
        
        //方法交换
        method_exchangeImplementations(thod1, thod2);
        [c1 run];
        
        //遍历方法
        unsigned int count ;
       Method *methods = class_copyMethodList(c1.class, &count);
        for (int i = 0 ; i<count; i++) {
            Method method = methods[i];
            NSLog(@"%@---",NSStringFromSelector(method_getName(method)));
        }
        //添加方法
        class_addMethod(c1.class, @selector(running), (IMP)running, "v@:");
        [c1 performSelectorOnMainThread:@selector(running) withObject:nil waitUntilDone:YES];

实际应用:如防止button重复点击

+ (void)load{
    
    Method thod1 = class_getInstanceMethod([self class], @selector(sendAction:to:forEvent:));
    Method thod2 = class_getInstanceMethod([self class], @selector(My_sendAction:to:forEvent:));
    method_exchangeImplementations(thod1, thod2);
    
}

- (void)My_sendAction:(SEL)action to:(nullable id)target forEvent:(nullable UIEvent *)event{
    if (self.avoidDoubleCick == NO) {
        self.avoidDoubleCick = YES;
        [self My_sendAction:action to:target forEvent:event];
        [self performSelector:@selector(setAvoidDoubleCick:) withObject:@(NO) afterDelay:2];
    }
}

- (void)setAvoidDoubleCick:(BOOL)avoidDoubleCick{
    objc_setAssociatedObject(self, @selector(avoidDoubleCick), @(avoidDoubleCick), OBJC_ASSOCIATION_ASSIGN);
}

- (BOOL)avoidDoubleCick{
    return [objc_getAssociatedObject(self, @selector(avoidDoubleCick))boolValue];
}

数组防止加入空对象

@implementation NSMutableArray (extension)

+(void)load{
    Class cls = NSClassFromString(@"__NSArrayM");
    Method method1 = class_getInstanceMethod(cls, @selector(insertObject:atIndex:));
    Method method2 = class_getInstanceMethod(cls, @selector(my_insertObject:atIndex:));
    method_exchangeImplementations(method1, method2);
}

- (void)my_insertObject:(id)anObject atIndex:(NSUInteger)index{
    if(anObject== nil)return;
    [self my_insertObject:anObject atIndex:index];
}

@end

• Foundation框架有一些类型实质上和看到的不一样(类簇),可以输出class看出其真实类型从而进行方法交换.
• 方法交换实质上IMP的交换,并且会清空之前的缓存.