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operator<<= in tree control reference example [message #30497]

Wed, 05 January 2011 10:55

gprentice
Messages: 260
Registered: November 2005
Location: New Zealand

Experienced Member

In the tree control reference example there is this code

   void LoadTree(int parent, const String& path, Progress& pi)
   {
      pi.SetText(DeFormat(path));
      for(FindFile ff(AppendFileName(path, "*.*")); ff; ff.Next()) {
         if(pi.StepCanceled())
            return;
         String n = ff.GetName();
         if(n != "." && n != "..") {
            edit.Add();
            edit.Top() <<= n;

Why does the last line use operator<<= instead of operator= ?

If there's no reason then it should be changed to operator= because it took me a while to track down the fact that it seems to go through Ctrl::operator<<= which goes through the SetData virtual function into EditField::SetData. For a newcomer or even not for a newcomer, it's not easy to find what that operator<<= does - it doesn't make any sense to use it in an example.

Also, why does the above code do an unnecessary call to the Top() function - couldn't it just be edit.Add() = n;

And lastly (off topic but related to the edit.Add function call), does U++ assume that memory allocation with new never fails - how does U++ handle failure?

Graeme

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