Invalid use of incomplete type “class…”

Question

I keep getting this error and I don\'t understand what I do wrong: \" error: invalid use of incomplete type \'class Auftrag\'\" at method getAuftrae

Answer 1

Place the function definitions after the definition of the class Auftrag.

For example

inline void  Kunde ::addAuftrag(Auftrag *auftrag){
    this->vpa.push_back(auftrag);
}

inline void  Kunde ::getAuftraege() {
    for (int i{0};i<vpa.size();i++)
        cout << this->vpa.at(i)->getID();
}

The compiler has to know the definition of the class Auftrag that to determine that it has such a data member as vpa.