Compile error associated with std::unique_ptr and abstract classes - c++

Question

I have class that inherits from a base class. The base class contains pure virtual functions that are overridden in the derived class. I instantiate the base class object with std::unique_ptr of the derived class but get a compile time error
class Base {
public:
~Base () = default;
initBase () { count = 0; }
virtual void method1() = 0;
virtual void method2() = 0;
private:
int count;
};
class Child final : public Base {
public:
Child() = default;
~Child() = default;
void method1() override { std::cout << "B Running method 1\n"; }
void method2() override { std::cout << "B Running method 2\n"; }
};
class myClass {
public:
myClass(std::unique_ptr<Base> base) { _base(std::move(base)) };
~myClass() = default();
private:
std::unique_ptr<Base> _base;
};
int main() {
myClass obj = myClass(std::make_unique<Child>());
}
Compiler gives the following error:
error: invalid new-expression of abstract class type 'Base'
{ return unique_ptr<_Tp>(new _Tp(std::forward<_Args>(__args)...)); }
because the following virtual functions are pure within 'Base':
class A {
'virtual void Base::method1()'
virtual void method1() = 0;
'virtual void Base::method2()'
virtual void method2() = 0;

Answer 1

There are several typos in your code:
In Base:
Change
initBase () { count = 0; }
to
Base () { count = 0; }
In Child:
change
myClass(std::unique_ptr<Base> base) { _base(std::move(base)) };
to
myClass(std::unique_ptr<Base> base) : _base(std::move(base)) { }
change
~myClass() = default();
to
~myClass() = default;
In main():
change
myClass obj = myClass(std::make_unique<Child>());
to
myClass obj(std::make_unique<Child>());
#include <iostream>
#include <memory>
class Base {
public:
~Base () = default;
Base () { count = 0; }
virtual void method1() = 0;
virtual void method2() = 0;
private:
int count;
};
class Child final : public Base {
public:
Child() = default;
~Child() = default;
void method1() override { std::cout << "B Running method 1\n"; }
void method2() override { std::cout << "B Running method 2\n"; }
};
class myClass {
public:
myClass(std::unique_ptr<Base> base) : _base(std::move(base)) { }
~myClass() = default;
private:
std::unique_ptr<Base> _base;
};
int main() {
myClass obj(std::make_unique<Child>());
std::cout << "OK";
}
With those fixes in place, the code compiles fine.
Live Demo