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[Mister Zimbu]

Too used to Java (which does OO *right* ... I can't get this working:

class Parsable {
  public:
   virtual void parse();
};

class Token: public Parsable {
  public:
    void parse();
    Token( string id );
    string getId();

  private:
    string id;
};

There are other classes that also inherit from parsable.
Later on, I have a vector of children of Parsables (no Parsables themselves). I want to iterate through the list, and do some checks on their properties. From those checks I can determine whether it's a Token or not. One of the things I want to do is get the id of the token (through getId).

The problem is, how do I convert the Parsable to a Token and maintain all the internal data? In Java it's easy, i can just say:

Token t = parsableList.at(i);

Or in the worst case scenario I can typecast it there:

Token t = (Token)(parsableList.at(i));

No luck in C++ though. Both give me errors.

I tried giving a getId() function to Parsable, but when I do that and call it. the Token's getId function won't override it.

Any suggestions?

 

[Lathentar]

You need to use pointers.

Parsable *p = new Token("MONKEY FUCKER");
Token *t = static_cast<Token>(parse);

 

[Chairman85]

I don't think you need to static cast.

p->parse() should work.

 

[NohWun]

Too used to Java (which does OO *right* ... I can't get this working:
...snip...
I tried giving a getId() function to Parsable, but when I do that and call it. the Token's getId function won't override it.

Any suggestions?

Make the getId() function virtual. You need something like that in order to differentiate the Parsables.

 

[Jesiatha]

Not being able to do the conversion is the right thing, since a Parsable is not a Token. As mentioned, you can use RTTI's static_cast or dynamic_cast to get around it. Or you could add virtual methods to Parsable, as appropriate. Or create a new class which has members of the different subtypes of Parsable, and then do a switch based on that. Either way, what you're doing now is subverting the typing system, and is bad.

edit - accidentally posted mid writeup