c++ - 未处理的异常:访问冲突读取位置

test.exe中0x001AF3B5处未处理的异常：0xC0000005：访问冲突读取位置0x00000000。

在项目http://sourcemaking.com/design_patterns/command/cpp/2中实现此代码时遇到未处理的异常

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

class Command
{
// 1. Create a class that encapsulates an object and a member function
// a pointer to a member function (the attribute's name is "method")
Person *object; //
void(Person:: *method)();
  public:
    Command(Person *obj = 0, void(Person:: *meth)() = 0)
{
    object = obj; // the argument's name is "meth"
    method = meth;
}
void execute()
{
    (object-> *method)(); // invoke the method on the object
}
};

class Person
{
string name;

// cmd is a "black box", it is a method invocation
// promoted to "full object status"
Command cmd;
  public:
Person(string n, Command c): cmd(c)
{
    name = n;
}
void talk()
{
    // "this" is the sender, cmd has the receiver
    cout << name << " is talking" << endl;
    cmd.execute(); // ask the "black box" to callback the receiver
}
void passOn()
{
    cout << name << " is passing on" << endl;

    // 4. When the sender is ready to callback to the receiver,
    // it calls execute()
    cmd.execute();
}
void gossip()
{
    cout << name << " is gossiping" << endl;
    cmd.execute();
}
void listen()
{
    cout << name << " is listening" << endl;
}
};

int main()
{
  // Fred will "execute" Barney which will result in a call to passOn()
  // Barney will "execute" Betty which will result in a call to gossip()
  // Betty will "execute" Wilma which will result in a call to listen()
  Person wilma("Wilma", Command());
  // 2. Instantiate an object for each "callback"
  // 3. Pass each object to its future "sender"
  Person betty("Betty", Command(&wilma, &Person::listen));
  Person barney("Barney", Command(&betty, &Person::gossip));
  Person fred("Fred", Command(&barney, &Person::passOn));
  fred.talk();
}

完全不确定为什么？我实现了它，因为它没有任何变化，只是输出有所不同，只有2​​个人而不是4个人。尝试了一些调试及其在命令中execute（）时的错误。

任何帮助或技巧都将非常有用！

编辑：实际上，在经过一些测试之后，当我更改人员和发生的呼叫时，不确定为什么。

    Person player("Player", Command());
    Person master("House Master", Command(&player, &Person::passOn));
    master.talk();

最佳答案

问题在于您允许使用空命令，甚至可以不检查就执行它。

将Command的构造函数更改为此可以解决问题：

Command(Person &obj, void(Person:: *meth)())

关于c++ - 未处理的异常:访问冲突读取位置，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/19899546/