Deprecated behavior - why? - page 2

[Petr Nosek]

Alain Verleyen:
That's the fast fix, I am suggesting to think better about the design.

Of course, you are right and I agree with you.

[Doerk Hilger]

Thank you guys for enlightening me :)

[Doerk Hilger]

Petr Nosek:

The new behaviour means that the called parent method is hidden by the descendant method. You have to explicitly specify the instance of the called method in order to avoid a warning.

This won´t compile in MT4 so it´s not a good solution, when your code needs to be 100% compatible between both platforms. 

[Petr Nosek]

Doerk Hilger:

This won´t compile in MT4 so it´s not a good solution, when your code needs to be 100% compatible between both platforms. 

If you need same-named functions in both classes you have to use this design IMO that can be compiled both in MQL5 and MQL4:

class CBase
   {
      public:
      bool Text(string text, int index=0) { return true; }
      string Text(int index=0) { return "CBase"; }
   };
   
class CDev : public CBase
   {
      public:
      string Text(string text1, string text2) { return "CDev"; }
      string Text(int index=0) { return CBase::Text(index); }
   };

void OnStart()
  {
   CDev dev;
   string value=dev.Text();
   Print(value);
  }

[Alain Verleyen]

Petr Nosek:

Of course, you are right and I agree with you.

Actually I was wrong, it depends of the situation. The simple fix using scope operator can be the right solution or not.

Example:

class CBase
  {
   int               rawdata[];
public:
                     CBase(void) { /*...*/ };
                    ~CBase(void) {};

   void              Load(string filename)
     {
      /* save raw data */
     }
  };
class CDerived : public CBase
  {
   string            filename;
public:
                     CDerived(void) { filename="..."; };
                    ~CDerived(void) {};

   void              Load(void)
     {
      CBase::Load(filename);      // deprecated behavior fixed simply with CBase::

      /*
         some stuff
      */
     }
  };
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
   CBase base;
   base.Load("base...");      // Ok

   CDerived derived;
   derived.Load("derived..."); // deprecated behavior... Is actually a logical error Load() should be used.
  }

The Base class can be used standalone, so the load method with a filename parameter is fine.

In the derived class, I have a load method which is a kind of wrapper on the CBase Load method. However on a derived object I don't want the CBase Load method to be callable as it would lead to logical error, so I used intentionally the "hidden method".

Inside CDerived the simple fix is what is needed, and outside I get the warning, reminding me it's a logical error the call this version of the Load() method.

On other case, a redesign would be needed, all depends of the semantic, which is not obvious with meaningless example using Text() method.