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colin-home merged 1 commit into from
May 29, 2020
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Whitespace at cpp/pointers-to-members.md #2230

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38 changes: 20 additions & 18 deletions docs/cpp/pointers-to-members.md
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Original file line number Diff line number Diff line change
Expand Up @@ -55,8 +55,8 @@ class Window
public:
Window(); // Default constructor.
Window( int x1, int y1, // Constructor specifying
int x2, int y2 ); // window size.
bool SetCaption( const char *szTitle ); // Set window caption.
int x2, int y2 ); // Window size.
bool SetCaption( const char *szTitle ); // Set window caption.
const char *GetCaption(); // Get window caption.
char *szWinCaption; // Window caption.
};
Expand All @@ -71,23 +71,24 @@ int main()
In the preceding example, `pwCaption` is a pointer to any member of class `Window` that's of type `char*`. The type of `pwCaption` is `char * Window::*`. The next code fragment declares pointers to the `SetCaption` and `GetCaption` member functions.

```cpp
const char * (Window::*pfnwGC)() = &Window::GetCaption;
bool (Window::*pfnwSC)( const char * ) = &Window::SetCaption;
const char * (Window::* pfnwGC)() = &Window::GetCaption;
bool (Window::* pfnwSC)( const char * ) = &Window::SetCaption;
```

The pointers `pfnwGC` and `pfnwSC` point to `GetCaption` and `SetCaption` of the `Window` class, respectively. The code copies information to the window caption directly using the pointer to member `pwCaption`:

```cpp
Window wMainWindow;
Window wMainWindow;
Window *pwChildWindow = new Window;
char *szUntitled = "Untitled - ";
int cUntitledLen = strlen( szUntitled );
int cUntitledLen = strlen( szUntitled );

strcpy_s( wMainWindow.*pwCaption, cUntitledLen, szUntitled );
(wMainWindow.*pwCaption)[cUntitledLen - 1] = '1'; //same as
//wMainWindow.SzWinCaption [cUntitledLen - 1] = '1';
(wMainWindow.*pwCaption)[cUntitledLen - 1] = '1'; // same as
// wMainWindow.SzWinCaption [cUntitledLen - 1] = '1';
strcpy_s( pwChildWindow->*pwCaption, cUntitledLen, szUntitled );
(pwChildWindow->*pwCaption)[cUntitledLen - 1] = '2'; //same as //pwChildWindow->szWinCaption[cUntitledLen - 1] = '2';
(pwChildWindow->*pwCaption)[cUntitledLen - 1] = '2'; // same as
// pwChildWindow->szWinCaption[cUntitledLen - 1] = '2';
```

The difference between the **`.*`** and **`->*`** operators (the pointer-to-member operators) is that the **`.*`** operator selects members given an object or object reference, while the **`->*`** operator selects members through a pointer. For more information about these operators, see [Expressions with Pointer-to-Member Operators](../cpp/pointer-to-member-operators-dot-star-and-star.md).
Expand Down Expand Up @@ -131,24 +132,24 @@ using namespace std;

class Base
{
public:
public:
virtual void Print();
};
void (Base ::* bfnPrint)() = &Base :: Print;
void Base :: Print()
void (Base::* bfnPrint)() = &Base::Print;
void Base::Print()
{
cout << "Print function for class Base\n";
cout << "Print function for class Base" << endl;
}

class Derived : public Base
{
public:
public:
void Print(); // Print is still a virtual function.
};

void Derived :: Print()
void Derived::Print()
{
cout << "Print function for class Derived\n";
cout << "Print function for class Derived" << endl;
}

int main()
Expand All @@ -162,6 +163,7 @@ int main()
(bPtr->*bfnPrint)();
}

//Output: Print function for class Base
Print function for class Derived
// Output:
// Print function for class Base
// Print function for class Derived
```