Question

I am currently learning OOP for a project I’m working on (I’m in highschool and have some experience with c++; this is my third ‘large’ (>3 months) c++ project.) I have the basics of C++ classes figured out and managed to make some of the classes for the project.

So these is my page.h header:

class cl_Page{
public:
  cl_Page(cl_LessonMoment *parent_param);
  cl_Page(cl_SoftRoot *parent_param);
  int parent_type;
  cl_LessonMoment *parent_lmoment;
  cl_SoftRoot *parent_softroot;

  char id[256];

  //<content>
  //Backgrounds.
  str_Color bgcolor;
  cl_Image bgimage;

  //Actual content
  vector<cl_Textbox> textboxes;
  vector<cl_Button> buttons;
  vector<cl_Image> images;
  //</content>
};

(include guards and such are not here, but they are in my project)

And this is my page.cpp:

cl_Page::cl_Page(cl_LessonMoment *parent_param){
  parent_lmoment = parent_param;
  parent_type = 1;
  id[0] = '\0';
  //bgimage(NULL);
  SetColor(bgcolor, 0x000000ff);
}

(the other constructor is similar, it just sets a different type of parent)

My problem is that I want to call the constructor to bgimage (which is of cl_Image class type) inside my cl_Page constructor. If I try this (uncomment the line in the constructor), obviously it won’t work.

So yeah, how do I call the constructor now? I really need to construct every member along with the cl_Page object.

Answer 1

If you want to create bgImage object in cl_Page constructor, it has to be either a pointer (1) or you should use a constructor’s initialization list (2), which in this case would probably be a better solution for you.

1. – Field is a pointer to cl_Image

bgImage = new cl_Image(nullptr);

2. – Use of constructor’s initialization list

cl_Page::cl_Page(cl_LessonMoment *parent_param) :
      bgImage(nullptr) 
{
  parent_lmoment = parent_param;
  parent_type = 1;
  id[0] = '\0';
  SetColor(bgcolor, 0x000000ff);
}

There you can read more about constructor’s initialization list: http://www.cprogramming.com/tutorial/initialization-lists-c++.html