1

Topic: Templates

Dear programmers at me a question
Here we tell there is a structure of classes

<class Color>
class AbstractCar {
}
class BMW: AbstractCar <Black> {
}
class Porshe: AbstractCar <White> {
}
std:: vector <AbstractCar> cars;
BMW car1;
Porshe car2;
cars.emplace_back (car1);
cars.emplace_back (car2);

With ++ swears?
Whether I can so to operate with templates and a vector?
Thanks.
[mod the version. [/mod]

template <class Color>
class AbstractCar {
};
class BMW: AbstractCar <Black> {
};
class Porshe: AbstractCar <White> {
};
std:: vector <AbstractCar> cars;
BMW car1;
Porshe car2;
cars.emplace_back (car1);
cars.emplace_back (car2);

2

Re: Templates

template <class Color>
class AbstractCar {
}

3

Re: Templates

semen.s.semen wrote:

Whether I can so to operate with templates and a vector?
Thanks.

No. Even if it also would not be a template,  base class on value in a vector would conduct to object slicing'.
Get a basic not sample basic (abstract) class for AbstractCar and store its pointers in a vector.

4

Re: Templates

--Get a basic not sample basic (abstract) class for AbstractCar and store its pointers in a vector.
And with sample so it is impossible?

5

Re: Templates

semen.s.semen wrote:

And with sample so it is impossible?

No because, formally, the template type is not. The type which will be stored in it, at least, for calculation of its size is necessary to a vector.
The template class becomes type only at it  in specific sample parameters.

6

Re: Templates

Clearly
Thanks

7

Re: Templates

template <class Color>
class AbstractCar {
};
class BMW: AbstractCar <Black> {
};
class Porshe: AbstractCar <White> {
};
std:: vector <AbstractCar> cars;
// here does not give the chance storages in one container of values of different types, polymorphicly.
//that it to make, it is necessary to store under the link, in the form of the pointer. Only then the polymorphic type can be stored.
BMW car1;
Porshe car2;
cars.emplace_back (car1);
cars.emplace_back (car2);

It is possible to use
std:: vector <std:: unique_ptr <Car>> or
std:: vector <std:: shared_ptr <Car>>
Besides, sample AbstractCar also does this work .
Types
class BMW: AbstractCar <Black>
class Porshe: AbstractCar <White>
with each other, they do not have general ancestor.
Because
AbstractCar <Black> and AbstractCar <White> - different data types , in any way  with each other classes.
Therefore in base class also it is necessary to get rid of a template.
But fortunately the template here just is not necessary on figs, AbstractCar it is necessary to make , and color - is simple it  (property) and to set it for example in the designer.