我将一个变量分配给存储在指针地址中的值，那么为什么当初始值改变时它不改变呢？

Question

Basically, I just want to know why 'C' doesn't change when 'A' does. I'm guessing that it's because of the hierarchy, but I wanted to confirm and get an explanation as to why...

#include <iostream>
using namespace std;

class IntCell
{
public:
  explicit IntCell( int initialValue = 0 )
  { storedValue = new int{ initialValue }; }
  
  int read() const
  { return *storedValue; }
  
  void write( int x )
  { *storedValue = x; }
  
private:
  int *storedValue;
};

int main() {
  IntCell a{ 2 };
  IntCell* b = &a;
  IntCell c;
  
  int x = 10000;
  int* y = &x;
  
  cout << *y << endl;
  
  c = *b;
  
  a.write(4);
  cout << a.read() << endl << c.read();
  return 0;
}

Answer 1

I test your code and when you change "a", "c" change too. Also You need to implement a copy constructor and assignment operator.

IntCell c; // you create a new instance with new memory address.

c = *b; // now this instance point to same memory as "a".

a.write(4); // so when you change "a", "c" change too.

Answer 2

1. In your case, the destructor is missing.

    ~IntCell(){ cout<<"deleting...\n"; delete storedValue; }

2. You are using the implicitly-defined copy assignment. That is why c = *b; works. After the copy assignment, IntCell c and IntCell a both have the member which points to the same location. If a.write(4) , c.read() will get the same value 4 .