Can and how do I extend an array of objects during run time?

Can and how do I extend an array of objects during run time?

• blemmon

  This is a List Control(ListView) with unknow number of listing until run time when I load it up and it could be a few listing or a couple hundred of listing...

  Any way to dynamically add new object to anarray of objects(or sturct type variable)

  Thanks.

  
  
  

• IceX

  This is how I declare initially,

  userData = new CUserContextData[numOfChecks];

  There is a listview(with checkboxes) control in my dialog window. When user checks additional listing item then I would need to create an additional userData object each time to hold the data coorsponding to that checked item. (Oh, I am yet to change from array to vector)

  My question is how do I declare this new item I mean, I can't use the same name over and over now can I

  
  
  

• pven

  Hi, I've been working on other part of the project but this problem still exist for me. I was wondering, would vector store a class object that I defined which mainly to hold some data for me. I suspect it might be a sytax problem Becuase all the example I've seen on msdn using only the intergers like v.push_back(10);

  How do I pass an object to it
  userDataObjects.push_back(&newUserData);
  That is not working becuase compiler comes back complaining that it expects
  the arg to be of type :
  
  error C2664: 'std::vector<_Ty>::push_back' : cannot convert parameter 1 from
  'CUserContextData *' to 'const CUserContextData &'

  p.s., my class object has several members that are declare as wchar_t*. So, it's not just a simple varible or a constant number.
  
  Thank you.
  

  
  
  

• tonyinbeijing

  Can you not use conditional statements to name objects that correspond to each checkbox That would solve that problem I think.

  i.e. if(checkbox1->selected==true)

  
  

• Harendra Singh

  I'm getting Assertion error with the following line of code. Can anyone see what I'm doing wrong here Thanks.

  vector <CUserContextData> userDataObjects;

  vector<CUserContextData>::iterator userDataIter;

  userDataObjects.push_back(newUserData);

  
  
  

• Joseph Kasende

  Many thanks to all that reply and gave help. I will now try that in my code. Thank you guys!
  
  

• Craig Guyer - MSFT

  I don't quite understand your question, but this is how I'll answer it ;)

  If you can do it for an int, then you can do it for vector...

  
  

• lchase4411

  One more question about this. Since this is unknow number of objects that I'm adding. How can I do the declaration for each new object It would be like <myClass> whatobjectname Can the object name be a string variable Thanks.
  
  

• karls123

  Hi Thankk you for the reply. I open the #include<vector> and found

  void push_back(const _Ty& _Val)

  Do I change it to : void push_back(const _Ty* _Val)

  if not, then where and how do I change the template that you're referring to

  Also, below is my class definition, statement of instantiate an object of that class and a smaple of how I allocate memory for one of the member data. Do I need to create a Copy menthod for my class, otherwise, how does vector knows how to make a copy of my data

  Thank you.

  class CUserContextData

  {

  public:

  CUserContextData(void)

  {

  }

  virtual ~CUserContextData(void)

  {

  if(wcslen(shell) >0)

  delete [] shell;

  if(wcslen(homeDir) >0)

  delete [] homeDir;

  if(wcslen(primaryGroup) >0)

  delete [] primaryGroup;

  if(wcslen(symarkUserRef) >0)

  delete [] symarkUserRef;

  if(wcslen(LoginName) >0)

  delete [] LoginName;

  }

  public:

  bool newObject, bWinLogOn, bUnifiedID, symarkEnabled, UIDChanged;

  wchar_t *shell, *homeDir, *primaryGroup, *symarkUserRef, *LoginName, *contextName;

  LPCWSTR lpcwContextName;

  int symarkUID, listViewIndex, UID;

  };

  /////////////////////////////////////////////

  CUserContextData *newUserData = new CUserContextData;

  /////////////////////////////////////////////

  //Get the Shell

  hResult =ptSyUserObject->Get(CComBSTR("symark-Shell"), &var);

  if(FAILED(hResult))//New Sy User

  {

  DisplayError( hResult, L"Error obtaining symark-Shell. - RetrieveUserAtt");

  goto CleanUp;

  }

  temp = var.bstrVal;

  if(temp.length()>0)

  {

  lpcTemp = temp;

  newUserData->shell = new wchar_t[wcslen(lpcTemp)+1];

  wcscpy(newUserData->shell, (lpcTemp));

  }

  else

  newUserData->shell =NULL;

  VariantClear(&var);

  
  
  

• mmmattias

  Here's an example for you... I like examples when I'm not sure what to do...

  //include this...

  #include <vector>

  std::vector<myClass> anyObjects; //That's it to declare it!

  std::vector<myClass>::iterator aOi; //this is what we're going to use to navigate through our vector

  //Adding objects to the vector. Push back adds the object to the end of the vector

  anyObjects.push_back(myObject1);

  anyObjects.push_back(myObject2);

  anyObjects.push_back(myObject3); //etc

  //A method of getting at the objects

  for(aOi = anyObjects.begin(); aOi!= anyObjects.end(); aOi++)

  {

  myTempObject = aOi;

  }

  //Another method of getting at the objects

  myTempObject = anyObjects.front(); //gets the first object in vector

  myTempObject = anyObjects.back(); //gets the last object in vector

  I hope this helps...

  Ljubica

  
  

• Tim Greenwood

  Hey, the template parameter type is different with the type of the object you passed to push_back, one is reference type, one is pointer type

  remove the & in the push_back statement to pass reference.or you can change the template parameter of std::vector from CUserContextData& to CUserContextData*

  
  
  

• grissett

  Have you thought of using a linked list instead. That is to have the object contain a pointer to the next object that gets created at run time.

  Thanks,

  Ayman Shoukry

  VC++ Team

  
  
  

• Derek Lan

  As light walker says, you should really consider using one of the standard container types. I strongly suggest using std::vector. It offers syntax equivalent to builtin arrays, but can grow as needed. You can eighter add elements as you go (using push_back) or resize at once to the expected final size (using resize), growing and shrinking as many times as you want. You can pass a pointer to it's first element (&myvector[0]) to any function expecting a pointer to the first element of an array. You also don't have to worry about calling delete [] when you done with it (assuming you allocated it on the stack).
  
  Cheers,
  
  ::Camelo
  
  

• vito1281

  you can try vector or list, they are nice to manage unknown number of objects.
  
  
• Can and how do I extend an array of objects during run time?