pointers to objects in lists

[Jordan C Atlas]

class classA { public: //uses push_back to add a new Object to objectList addObject(Object newObject); private: list objectList; }; class classB { private: classA* Aptr; void addObjectToClassA(); }; void ClassB::addObjectToClassA() { Object newObject(); Aptr->addObject(newObject); } Hello all, I have what is probably a simple question, but I've been wrestling with it for a while. I have code that looks like what I typed above. classA has an std::list of Objects. classB has a method that will add a new Object to that list in classA. As I understand it, it creates a copy of the Object and the copy is what is added to the list. How can I iterate over objectList and actually modify the objects in the list? When I iterate now it seems that the Objects in the list are not modified... It seems that copies are modified instead. I thought one option would be to make objectList a list of pointers to Objects instead... But what will happn when I add an object to the list in classB? If I create a local Object* and add that to the objectList, does the pointer get added or does a copy of the pointer get added? (I'm just worried that the pointer won't refer to anything after addObjectToClassA() exits). Thanks! -Jordan Atlas

[Christian Graus]

I don't believe that a copy is made when you add something to a list, but either way, if a pointer is copied, it still points to the same memory address. Christian I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

[Jordan C Atlas]

Christian Graus wrote: but either way, if a pointer is copied, it still points to the same memory address. Yes, but if I have a function like this: void ClassB::addObjectToClassA() { Object* newObject; Aptr->addObject(newObject); } What happens after the function exits? Does the pointer point to anything (sensible) anymore? Thanks, -Jordan Atlas

[Christian Graus]

No, it never pointed to anything sensible. Object * newObject = new Object(); NOW you have a pointer to something sensible, and you can make as many copies of that pointer as you like. Until you put delete newObject; it will continue to exist, and if you fail to ever call delete, you've got a memory leak. Christian I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

[markkuk]

If a STL list contains objects instead of pointers to objects, then objects added to the list get copied, just like with all other STL containers.

[Christian Graus]

Yeah, I realised after commenting that I'm too used to C# now. It's still the case that if you have an iterator, you can modify the object, and the object in the container will be modified, because you have a reference to the object in the container, right ? Christian I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer