Tech Tips

Listing 4 Policy-driven design of PopulateHelper

class PopulateHelper {

  // simple, because the interfaces for adding strings between
  // the two controls are orthogonal
  template <typename T>
  void fill(T &ctrl, std::vector<std::string> &strs) {
	ctrl.ResetContent();
	for (int ii=0; ii<strs.size(); ++ii)
	  ctrl.AddString(strs[ii]);
  }

  // a place-holder
  template <typename T>
  struct GetTextFromCtrlPolicy {};

  // specialization for the CComboBox control
  template <>
  struct GetTextFromCtrlPolicy<CComboBox> {
static CString GetText(CComboBox &ctrl, int iIndex) {
		CString retStr;
		ctrl.GetLBText(iIndex, retStr);
		return retStr;
	}
  };

  // specialization for the CListBox control
  template <>
  struct GetTextFromCtrlPolicy<CListBox> {
	static CString GetText(CListBox &ctrl, int iIndex) {
		 CString retStr;
		 ctrl.GetText(iIndex, retStr);
		 return retStr;
	}
  };

  // now it doesn't matter if this method is specialized on CComboBox
  // or CListBox, the correct call is resolved through the
  // GetTextFromCtrlPolicy struct.
  template <typename T>
  CString getData(T &ctrl, int iIndex) {
	CString data;
	data = GetTextFromCtrlPolicy<T>::GetText(ctrl, iIndex);
	return data;
  }

};