Class with different types

Question

I am working on a C++ ROS Project, which contains different classes, each containing a vector.

The difficulty is that the vectors can be of different types. For example:

class A{
    public
        .....
    private 
        std::vector<Class_C> List
}
class B{
    public  
        .....
    private 
        std::vector<Class_D> List
}

How could I achieve such task? I would like to find a way to simplify my code using templates, inheritances, and other language features.

What are you going to do with the lists? What is the purpose of all the other classes? — Mateen Ulhaq, Mar 15 '16 at 16:00

score 3 · Answer 1 · answered Mar 15 '16 at 15:13

3

Just use a template argument:

template <typename T>
class A{
    public
        .....
    private 
        std::vector<T> List;
}

This allows A to have a vector of any type:

A<Class_C> foo;
A<Class_D> bar;

answered Mar 15 '16 at 15:13

Hatted Rooster

35,759
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And if I want a B class which inherit from A, is it possible to lock the type ? if the B class can only have "Class_C" as typename for example – S. Perfees Mar 15 '16 at 15:38
@S.Perfees Perhaps you should rethink what you are doing. ["Composition over inheritance"](http://stackoverflow.com/questions/49002/prefer-composition-over-inheritance) – Mateen Ulhaq Mar 15 '16 at 15:59

score 1 · Accepted Answer · edited May 23 '17 at 12:31

Since I cannot comment because of my reputation I have to write an answer, but Gill Bates' answer could solve your issue even though you are not clear on what you want to accomplish. And to extend on his answer you could use inheritance based of his template class to ease your coding and force a type into your list (you would also need to change your list visibility to protected in this case):

class FooInt : public A<int>{
    public
        void print() { /* print List's content */ }
...
};

class FooString : public A<std::string>{
    public
        void print() { /* print List's content */ }
...
};

You use your classes this way:

FooInt hello;
hello.print(); // Would print list of int

FooString moto;
moto.print(); // Would print list of string

Note that the classes' names are written as Foo* only to help you understand that their underlying lists would contain the types written in the names, this could be your class B inheriting from the class A...

score 0 · Answer 3 · edited Mar 15 '16 at 15:57

0

Is that what you are looking for?

template <typename T>
class A {
    public:
        .....
    protected: 
        std::vector<T> List;
};

class B : public A<Class_D> {
    public:
    .....
};

B b;

edited Mar 15 '16 at 15:57

Mateen Ulhaq

24,552
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answered Mar 15 '16 at 15:56

Obi1

38
4

Class with different types

3 Answers3