如何添加到静态 int +1

Question

如果我想在每次创建新机器人时更新我的静态 id 以id+=1，我该怎么做，在哪里？我试过这个，但它仍然不起作用

class Robot{
Robot(){
    static int id_count=0;
    id=id_count++;
}
int id;
int x;
int y;
}

Answer 1

一种方法可能是将其放置在构造函数中。

class Robot{
public:
    Robot() {
        static int id_count=0;
        id = id_count++;
    }
    int id;
    int x;
    int y;
}

Answer 2

你可以在构造函数中执行此操作：

class Robot {
    static int id;
    Robot() { ++id; }
    int x; 
    int y;
};

如果您希望每个机器人都有自己的 id，那么：

class Robot {
   static int refcount;
   int id;
   int x;
   int y;
   public:
     Robot() {
        id = ++refcount;
     }
}

Answer 3

创建一个static变量(不是id(，初始化它，并在构造函数中递增并分配给id。

工作和最简化的代码。

class Robot
{
    static int count;
    int id, x, y;
public:
    Robot()
    {
        id = count++;
    }
};
int Robot::count = 0;

完整的工作计划：

#include<iostream>
class Robot
{
    static int count;
    int id, x, y;
public:
    void show(){std::cout << id << std::endl;}
    Robot(){id = count++;}
};
int Robot::count = 0;
int main()
{
    Robot a, b, c;
    a.show();
    b.show();
    c.show();
    return 0;
}

你可以在这里运行

Answer 4

你需要在类中有一个静态的 int id，这样当创建Robot的另一个实例时，它也可以访问它。

#include <iostream>
using namespace std;
class Robot {
public:
  static int id;
  int x, y;
  // Give the class a constructor. This is called whenever a new instance of
  // Robot is created.
  Robot(int x, int y) {
    this -> x = x;
    this -> y = y;
    ++id;
    cout << "I am a new robot." << endl;
    cout << "My x value is " << x << endl;
    cout << "My y value is " << y << endl;
    cout << "My id is " << id << endl;
  }
};
int Robot::id = 0;
int main(int argc, char *argv[]) {
  // Create 5 new instances of robots and
  // say how many robots have been created.
  for(int i=0; i<5; ++i) {
    Robot r = Robot(1 * i, 1 * (i * 2));
    cout << "There are now " << r.id << " robots" << endl;
    cout << endl;
  }
  return 0;
}

输出：

I am a new robot.
My x value is 0
My y value is 0
My id is 1
There are now 1 robots
I am a new robot.
My x value is 1
My y value is 2
My id is 2
There are now 2 robots
I am a new robot.
My x value is 2
My y value is 4
My id is 3
There are now 3 robots
I am a new robot.
My x value is 3
My y value is 6
My id is 4
There are now 4 robots
I am a new robot.
My x value is 4
My y value is 8
My id is 5
There are now 5 robots