objective-c运行时机制runtime，动态获取对象的属性和成员变量

本文当中，利用oc的运行时机制，重写- (NSString *)description(类似于java的toString方法)来达到输出内容的目的。废话不多说，看代码

- (NSString *)description {

    NSMutableString *stringM = [NSMutableString stringWithFormat:@"
<%@: %p>
",self.class,self];
    
    //获取本类的clas
    Class cls = object_getClass(self);
    
    //输出参数，获取本类(不包括父类)成员变量总数
    unsigned int outCount = 0;
    
    //遍历本身和父类,并排除NSObject
    while (cls != NULL && cls != NSClassFromString(@"NSObject")) {
        
        //返回成员变量的的指针数组
        Ivar *ivars = class_copyIvarList(cls, &outCount);
        
        for (int i = 0; i < outCount; i++) {
            //拿到成员变量结构体指针
            Ivar ivar = ivars[i];
            //获得成员变量的名字
            NSString *ivarNameKey = [NSString stringWithUTF8String:ivar_getName(ivar)];
            //删除下划线(因为编译器自动为属性生成带_的成员变量)
            if ([ivarNameKey hasPrefix:@"_"]) {
                ivarNameKey = [ivarNameKey stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:@""];
            }
            //获取变量的值
            id value = [self valueForKey:ivarNameKey];
            
            [stringM appendString:[NSString stringWithFormat:@" %@ -> %@
",ivarNameKey,value]];
        }
        
        //释放指针
        free(ivars);
        
        //去父类中找
        cls = class_getSuperclass(cls);
    }
    
    return stringM;
}