+ +You should avoid having overloaded virtual methods in a base class because if +any of them is overriden in a derived class, then all others must be overriden +as well or it would be impossible to call them on an object of derived class. + +For example, the following code: + +
+ class Base
+ {
+ public:
+ virtual void Read(wxFile& file);
+ virtual void Read(const wxString& filename);
+ };
+
+ class Derived : public Base
+ {
+ public:
+ virtual void Read(wxFile& file) { ... }
+ };
+
+ ...
+
+ Derived d;
+ d.Read("some_filename"); // compile error here!
+
+
+will fail to compile because the base class function taking filename
+is hidden by the virtual function overriden in the derived class (this is
+known as [virtual] function name hiding problem in C++).
+
++The standard solution to this problem in wxWindows (where we have such +situations quite often) is to make both Read() functions not virtual +and introduce a single virtual function DoRead(). Usually, it makes +sense because the function taking a filename is (again, usually) implemented +in terms of the function reading from a file anyhow (but making only this +functions not virtual won't solve the above problem!). +
+So, the above declarations should be written as: +
+ class Base
+ {
+ public:
+ void Read(wxFile& file);
+ void Read(const wxString& filename);
+
+ protected:
+ virtual void DoRead(wxFile& file);
+ };
+
+ class Derived : public Base
+ {
+ protected:
+ virtual void DoRead(wxFile& file) { ... }
+ };
+
+
+This technique is widely used in many of wxWindows classes - for example,
+wxWindow has more than a dozen of DoXXX() functions which
+allows to have many overloaded versions of commonly used methods such as
+SetSize()
+
Some compilers don't pay any attention to extra semicolons on top level, as in