Creating a std::vector of derived classes-CodePudding

Assume that I have an Abstract Class

class AbstractClass {
public:
    virtual int get() const = 0;
};

and two different Derived classes

class DerivedClassA : public AbstractClass {
public:
    int get() const override { return 1; }
};

class DerivedClassB : public AbstractClass {
public:    
    int get() const override { return 2; }
};

and I want to pass a std::vector of Abstract Classed to a given function:

int f(const std::vector<std::shared_ptr<AbstractClass> >& classes) { ... }

What I'm doing is this:

int main () {
    std::vector<std::shared_ptr<AbstractClass> > _classes;
    std::shared_ptr<AbstractClass> _derivedA = std::make_shared<DerivedClassA>();
    _classes.push_back(_derivedA);
    std::shared_ptr<AbstractClass> _derivedB = std::make_shared<DerivedClassB>();
    _classes.push_back(_derivedB);
    std::cout << f(_classes) << "\n";
}

It does work but I'm wondering if there is a more compact form to write it in modern C ? I've tried using auto in some places but it always gives an error, or to build the derived classes in place, but it doesn't work as well.

CodePudding user response：

It does work but I'm wondering if there is a more compact form to write it

You could get rid of the intermediate variables to make it more compact:

f({
    std::make_shared<DerivedClassA>(), 
    std::make_shared<DerivedClassB>(),
});

Since all access specifiers are public, you can make the class definitions more compact by using struct:

struct DerivedClassB : AbstractClass {
    int get() const override { return 1; }
};

CodePudding user response：

Besides what @eeronika is suggesting, you can also implicitly call std::shared_ptr constructor by passing raw pointers:

int main () {
    std::vector<std::shared_ptr<AbstractClass> > _classes;
    _classes.emplace_back(new DerivedClassA);
    _classes.emplace_back(new DerivedClassB);
    std::cout << f(_classes) << "\n";
}