How does a virtual function impact constructor

Question

I am in the process creating a game and I have a problem. When I put in a “virtual” keyword to the function constructor just stops working:(

System Windows 11, C++23

Edit: You can not use braces with a class that has virtual functions. Is there a way to not generate a definition in parent class, but define in child class?

Vlad from Moscow · Answer 1 · 2022-10-07T19:40:40.567

1

You are trying to initialize an object of the class notworks as an object of an aggregate. But when a virtual function is declared then the class is not an aggregate.

From the C++ 20 Standard (9.4.2 Aggregates)

1 An aggregate is an array or a class (Clause 11) with

(1.1) — no user-declared or inherited constructors (11.4.5),

(1.2) — no private or protected direct non-static data members (11.9),

(1.3) — no virtual functions (11.7.3), and

(1.4) — no virtual, private, or protected base classes (11.7.2).

edited Oct 07 '22 at 19:40

answered Oct 07 '22 at 19:35

Vlad from Moscow

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That is correct thank you! I s there a way to not generate a definition in parent class, but define in child class? – avary Oct 07 '22 at 19:39
@avary You can declare a pure virtual function in the base class. – Vlad from Moscow Oct 07 '22 at 19:41
Can you please elaborate on what that is? – avary Oct 07 '22 at 19:42
@avary For example virtual void f() = 0; – Vlad from Moscow Oct 07 '22 at 19:43
If I have an array of type A a[]. for example a[0] = B() where b is child class of class A, and I want to call a[0].foo(), will it call A::foo()? – avary Oct 07 '22 at 19:46
or does it need to be a pointer to call B::foo() – avary Oct 07 '22 at 19:49
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@avary You may not declare an array of objects of the base class and then to store an object of a derived class. You need to read a book on C++. If you have some other questions then feel free to ask them at SO. Comments are not designed to ask questions. – Vlad from Moscow Oct 07 '22 at 19:49
Is there a way I could do something similar then? – avary Oct 07 '22 at 19:51

How does a virtual function impact constructor

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