C ++中的类和变量范围 [英] Classes and variables scope in C++

问题描述

class car {
    int speed; 
    double position;

    public:
       car(int v,double d);
       int getspeed();
};

int car::getspeed() {
return speed;
}

car::car(int s, double x){
   speed=s;
   position=x;
}

即使我为car（int s，v）指定了不同的变量，为什么它有效吗？
i虽然应该给我一个编译时错误？

Even though i specified different variables for car(int s,v), why does it work? i though it should give me a compile time error?

此代码：它使用哪个变量？

this code:which var it uses?

class car {
    int speed; 
    double position;

    public:
       car(int speed,double time);
       int getspeed();
};

int car::getspeed() {
   return speed;
}

car::car(int speed, double position){
   speed=speed;
   position=position;
}

我认为可以使用全局变量，或者可以使用它吗？ t一定要说

I think the global variable might be used, or is it something you can't say certain about

推荐答案

car::car(int speed, double position){
   speed=speed;
   position=position;
}

在此函数定义中，它对类成员car :: speed不起作用和car :: position，因为您在函数参数列表中声明了本地int速度和double位置，因此它们隐藏了类成员变量。要正确执行此操作，您需要明确地这样说：

In this function definition, it does nothing with the class member car::speed, and car::position, because you declared the local int speed and double position in the function parameter list, they hide the class member variables. To do it properly, you need explicitly say so:

car::car(int speed, double position){
   this->speed=speed;
   this->position=position;
}

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