c++ - 调用非静态函数的重载括号运算符

Question

我有一个类可以读取/写入外部随机存取存储器。

.h文件:

class RAM {
private:
  bool Read(char *Buffer, size_t BytesToRead, uint32_t StartAddress);
  bool Write(char *Buffer, size_t BytesToWrite, uint32_t StartAddress);

  class proxy {
  private:
    size_t _index;
  public:
    proxy(size_t i);
    void operator=(char rhs);
    operator char();
  }

public:
  proxy operator[](size_t i);
};

.cpp 文件:

RAM::proxy RAM::operator[](size_t i) {
  return proxy(i);
}

proxy::proxy(size_t i) {
    _index = i;
}

void proxy::operator=(char rhs) {
  Write(&rhs, 1, _index);  // error
}

RAM::proxy::operator char() {
  char Buf[1];
  Read(Buf, 1, _index);   // error
  return Buf[0];
}

Read 和 Write 是处理对 RAM 的低级访问的函数。没有其他方法可以读取或写入 RAM。我尝试使用 proxy class in rvalue - how to implement assignment operator?但无法正确调整它:

error: cannot call member function 'bool RAM::Write(char*, size_t, uint32_t)' without object Write(&rhs, 1, _index)

error: cannot call member function 'bool RAM::Read(char*, size_t, uint32_t)' without object Read(Buf, 1, _index)

还有其他调用 Read 和 Write 的东西，所以我可能无法将它们设为静态。我还认为它们在创建 RAM 对象时已经实例化了。

Answer 1

多亏了 PeteBecker，我才能够想出一个工作代码。另外，我没有在最初的问题中提出问题，但我忽略了测试直接分配，结果证明这是一个不同的野兽。

class RAM {
private:
  // changed 1st arg to void*, because type doesn't really matter.
  bool Read(void *Buffer, size_t BytesToRead, uint32_t StartAddress);
  bool Write(void *Buffer, size_t BytesToWrite, uint32_t StartAddress);

  class proxy {
  private:
    size_t _index;
    RAM *_parentPtr;  // <-- added

  public:
    proxy(size_t i, RAM *ptr) {
      _index = i;
      _parentPtr = ptr;  // <-- added
    }  
    void operator=(char rhs) {
      Write(&rhs, 1, _index);  // works now
    }
    void operator=(proxy rhs) {  // new function for direct assignment
      char temp = rhs;
      Write(&temp, 1, _index);
    }
    operator char() const {
      char Buf[1];
      Read(Buf, 1, _index);   // works now
      return Buf[0];
    }
  }

public:
  proxy operator[](size_t i) {
    return proxy(i, this);
  }
};

我花了很长时间才弄清楚，我必须通过临时变量请求 rhs 的值才能执行 operator char() const。作为引用传递是行不通的。