CODEWITHSUNDEEP
c++listheader
user7884887
user7884887

Reputation:

C++ list Function return List

I have 2 Classes in ssservice.h:

class ssverbindungsdaten {
public:
    ssverbindungsdaten();
    ~ssverbindungsdaten();

    int id;
    string test;
};

class softswitch {
public:
    softswitch();
    ~softswitch();
    list<ssverbindungsdaten> holeAlleRohdaten();
};

My ssservice.ccp:

list<ssverbindungsdaten> softswitch::holeAlleRohdaten() {
    //ssverbindungsdaten * ssv = new ssverbindungsdaten;
    list<ssverbindungsdaten> *listTmp = new list<ssverbindungsdaten>;
    return *listTmp;
}

And my main.cpp:

int main() {
    std::cout << "Starte ...";

    softswitch *ss = new softswitch;
    list<ssverbindungsdaten> *liSSVVerbinngsdaten = new list<ssverbindungsdaten>();
    liSSVVerbinngsdaten = ss->holeAlleRohdaten();
}

But there is an error in main.cpp:

cannot convert ‘std::__cxx11::list<ssverbindungsdaten>’
  to ‘std::__cxx11::list<ssverbindungsdaten>*’
  in assignment
     liSSVVerbinngsdaten = ss->holeAlleRohdaten();

The list holeAlleRohdaten should be a lsit, containing all Classes ssverbindungsdaten.

That I can later loop trough the liSSVVerbinngsdaten in main.cpp, and get all Classes ssverbindungsdaten with the values (int id, string test).

Why can't I just assing the List liSSVVerbinngsdaten to ss->holeAlleRohdaten?

Upvotes: 0

Views: 6475

Answers (3)

Thomas Sablik
Thomas Sablik

Reputation: 16449

You should do what the others say about pointers, smart pointers, naming, ...

But your error is 

liSSVVerbinngsdaten = ss->holeAlleRohdaten();

liSSVVerbinngsdaten is a pointer to a list and ss->holeAlleRohdaten() returns a list. You can fix your program by returning a pointer

ssservice.h:

class ssverbindungsdaten
{
public:
    ssverbindungsdaten();
    ~ssverbindungsdaten();

    int id;
    string test;

};

class softswitch{
public:
    softswitch();
    ~softswitch();
    list<ssverbindungsdaten>* holeAlleRohdaten();

};

ssservice.ccp:

list<ssverbindungsdaten>* softswitch::holeAlleRohdaten(){

    //ssverbindungsdaten * ssv = new ssverbindungsdaten;

    list<ssverbindungsdaten> *listTmp = new list<ssverbindungsdaten>;

    return listTmp;

}

main.cpp:

int main(int argc, char *argv[])
{
    //TODO: Mulithreading
    std::cout << "Starte ...";

    softswitch *ss = new softswitch;

    list<ssverbindungsdaten> *liSSVVerbinngsdaten = new list<ssverbindungsdaten>();

    delete liSSVVerbinngsdaten;
    liSSVVerbinngsdaten = ss->holeAlleRohdaten();

    delete softswitch;
    delete liSSVVerbinngsdaten;
    return 0;
}

This answer is only to understand the error. As the others said you should avoid raw pointers and use smart pointers. If you work with raw pointers you should remember that to every new belongs a delete.

Upvotes: 1

Bo Persson
Bo Persson

Reputation: 92271

If you skip all the new and pointers, the code will be a lot simpler:

int main(int argc, char *argv[])
{
    //TODO: Mulithreading
    std::cout << "Starte ...";

    softswitch ss;

    list<ssverbindungsdaten> liSSVVerbinngsdaten = ss.holeAlleRohdaten();

    return 0;
}

C++ is not at all like Java or C#. The list class will handle all the heap allocations internally. You don't have to do that.

Upvotes: 0

Junos
Junos

Reputation: 68

list<ssverbindungsdaten> *listTmp = new list<ssverbindungsdaten>;

The "new" keyword in c++ actually allocates a new pointer, so you are manually allocating a pointer to a list of ssverbindungsdaten objects. If you want to create a default instance of the class or list just use

list<ssverbindungen> listTmp;

Edit: Also stop coding in german and uppercase your class names

Upvotes: 2

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