C ++没有合适的默认构造函数-没有参数的继承的模板构造函数

Question

I've looked at over a dozen qst's with the phrase no appropriate default constructor available in it but none help with my own problem.

It's a very basic C++ qst (as I'm still learning the ropes), so sorry in advance if your eyes are glazing over at it's simplicity. I am trying to inherit a class that has a templated constructor with no arguments. Such as:

class Base {
public:

template<class T>
Base() {
  T *t = this;
  //more irrelevant stuff
}

}

I've tried

class Derived : public Base {
public:
  Derived() : Base() {

  }
}

and

class Derived : public Base {
public:
  Derived() {

  }
}

to no avail. In both cases I get the error message no appropriate default constructor available . How to go about doing this? If this is not possible can you explain why?

It worked when I set up my constructor like template<class T> Base(T *t) (taking the template argument as a parameter).

ps In case it matters, in my code I am also inheriting Derived by another class.

Answer 1

there is no syntax for accessing the default constructor in

class blah_t
{
public:
    template< class other_t > blah_t() {}
};

there also some other ways to make the default constructor inaccessible, eg

class blah_t
{
public:
    blah_t() {}
    blah_t( int = 666 ) {}
};

as the holy standard explains it, constructors don't have names…

but, back to the original question, in order to be able to specify the template argument, you need some ordinary function argument that involves the template parameter type