Hi There, Why templated inline constructor cannot be called like

Question

C / C++

John

Hi There, Why templated inline constructor cannot be called like

code below ?

template<typename T>
class CDerived : public CBase<T>
{
public:
CDerived() : CBase() {}// error

}

0

06.05.2021

22 ответов

15 просмотров

John Автор вопроса

Pavel
You probably need to specify the type CBase<T>()

It is derived from CBase<T> and CBase<T>::CBase() is not templated.

0

06.05.2021

Pavel

John
It is derived from CBase<T> and CBase<T>::CBase() ...

Yes, but as far as I remember any time you refer to the base class, you need to specify the full type because CBase is still a templated class. Or you can make an alias inside your class using Base = CBase<T>; and use this Base as the type of the base class. https://ideone.com/BIpAjR

0

06.05.2021

John Автор вопроса

Pavel
Yes, but as far as I remember any time you refer t...

Do you know the article on standart ?

0

06.05.2021

Pavel

John
Do you know the article on standart ?

No, I don't know any good links about this unfortunately.

0

06.05.2021

Sunbro

John
Do you know the article on standart ?

nevertheless @gameraccoon is right on this topic you have to _fully_ specify the class

0

06.05.2021

Alejandro

Did you try CBase<T>::CBase() ?

0

06.05.2021

John Автор вопроса

Sunbro
nevertheless @gameraccoon is right on this topic ...

Why ? What is the purpose of ex: template<typename T> class CDerived : public CBase<T> { public: CDerived() : CBase<int>() {} }

0

06.05.2021

Kuntal M

John
Why ? What is the purpose of ex: template<typen...

The constructor would be CBase<T>, you are inheriting a templated class

0

06.05.2021

Sunbro

John
Why ? What is the purpose of ex: template<typen...

Why the fuck did you put int in there oO

0

06.05.2021

Kuntal M

Kuntal M
The constructor would be CBase<T>, you are inherit...

typical example could be found in the boost libraries, where you inject certain behaviour into your class like this

0

06.05.2021

Kuntal M

Kuntal M
typical example could be found in the boost librar...

like obtaining a shared reference to itself

0

06.05.2021

John Автор вопроса

Sunbro
Why the fuck did you put int in there oO

Wow. Answer to silence ?

0

06.05.2021

Pavel

John
Why ? What is the purpose of ex: template<typen...

For example if you for some reason using multiple inheritance of many CBase specializations the compiler wouldn't be able to guess what you mean.

0

06.05.2021

John Автор вопроса

Kuntal M
typical example could be found in the boost librar...

can you show which ?

0

06.05.2021

John Автор вопроса

Pavel
For example if you for some reason using multiple ...

nah constructor doesnt like any other method.

0

06.05.2021

Kuntal M

John
can you show which ?

Check any TCP server implementation using boost::asio

0

06.05.2021

Pavel

John
nah constructor doesnt like any other method.

Not sure what you mean. You proposing a way of calling a constructor that wouldn't make sense in some situations.

0

06.05.2021

John Автор вопроса

Pavel
Not sure what you mean. You proposing a way of cal...

you mean supplying argument to template parameter wouldnt make sense ?

0

06.05.2021

Pavel

John
you mean supplying argument to template parameter ...

I gave you an example when the compiler wouldn't be able to decide what constructor you want to call in this case. I'm pretty sure it's not why it's not implemented, and even not sure if it's never going to be implemented this way in future (we already have CTAD, this is not so far from it).

0

06.05.2021

John Автор вопроса

Pavel
I gave you an example when the compiler wouldn't b...

Have you done it before ? the multiple inheritance of many CBase specialization ? The reason why we have to supply template argument to call base ctor ?

0

06.05.2021

Pavel

John
Have you done it before ? the multiple inheritanc...

Not sure, maybe, I've edited a lot of strange code including some weird template monsters. I agree that's not a common case, but these cases also need to be accounted.

0

06.05.2021

Pavel · Accepted Answer

Pavel

You probably need to specify the type CBase<T>()

0

06.05.2021

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Hi There, Why templated inline constructor cannot be called like

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