一点基础知识

这里有sizeof，c++类的静态成员变量；再就是虚函数，以及申明的问题，字节长度的问题。

#include <iostream>
#include <string>
using namespace std;

class State
{
public:
    State(){}
    ~State(){;}
    State(const int sta, const int depth)
    {
        //count ++;
        this->sta = sta;
        this->depth = depth;
    }
    int SetDepth(const int depth)
    {
        this->depth = depth;
    }
    //virtual int getDepth() = 0;

    /*
    virtual int getDepth()
    {
        return depth;
    }
    */

    int getState()
    {
        return sta;
    }

    static int count;

private:
    int sta;
    int depth;
};

int State::count = 0; // init; if not , it comes error

int main(int argc, char *argv[])
{
    State state(12, 3);
    cout << "count " << state.count << endl;
    state.count = 12;
    cout << "count " << state.count << endl;
    cout << state.getState() << endl;
    cout << "size of int " << sizeof(int) << endl;
    cout << "size of State " << sizeof(State) << endl;
    string str("hello world");

    cout << str << endl;

    return 0;

}

记住类的静态成员需要初始化；相应的输出结果是：

count 0
count 12
12
size of int 4
size of State 8
hello world