CODEWITHSUNDEEP
c++functioninheritance
JimRaid
JimRaid

Reputation: 125

How to speak to a inherit class from another inherit class

Here to show you what I mean exactly it hard to describe without code:

class Object
{ 
      // attributes..
};

class Attribute
{
    public:
    void myfunc(); 
};

class Character: public Object, public Attribute
{ 

};

void main()
{
    Object* ch = new Character;
    // How can I call the myfunc() from Attribute
    // tried static_cast<Attribute*>(ch);
}

I only just have a Object Class pointer and i doesn't know if it is a Character Object or another object which inherit from the Attribute class, what i know is that the class inherit from Attribute Class.

Upvotes: 1

Views: 113

Answers (2)

Kerrek SB
Kerrek SB

Reputation: 477080

If you know that you have an object of the correct type, you can cast explicitly:

Object * ch = /* something that's a Character */

static_cast<Attribute *>(static_cast<Character *>(ch))->myfunc();

Obviously this will not be correct if the type of the most-derived object pointed to by ch is not a subtype of Attribute.

If your class hierarchy is polymorphic (i.e. has at least one virtual function in each base class that you care about), then you can use dynamic_cast directly at runtime and check if it succeeded, but that is a comparatively expensive operation. By contrast, the static cast does not incur any runtime cost at all.

Upvotes: 2

Edward Strange
Edward Strange

Reputation: 40859

Cross casting can only be done by dynamic_cast.

Object * o = new Character;
Attribute * a = dynamic_cast<Attribute*>(o);

if (!a) throw_a_fit();

a->myfunc();

However, for this to work you must have polymorphic base classes (they must have at least one virtual function).

Upvotes: 3

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