[Development] QFile: writing via a temporary file

[Oswald Buddenhagen]

On Thu, Jan 19, 2012 at 10:42:28PM +0100, ext David Faure wrote:
> Ah, but my "separate class" initial idea was the KDE/QtCreator idea, i.e. a 
> class that isn't a QFile. So deriving from QFile is a new idea :)
> 
well, creator's savefile is derived from qtemporaryfile, which makes the
implementation very elegant. but that's a minor detail.

> B) QFile builtin mode.
> Thiago's emails made me realize that this solution is only valid if no 
> additional API methods are needed (since otherwise we have methods that don't 
> make sense unless we're in a specific mode, so better put them in a subclass).
> But do we still need additional methods? The developer can ask close() to
> roll back by simply calling setError() on the file before closing, for errors 
> that QFile couldn't detect itself.
> 
one could do it that way, yes.
but for exception safety this means that the d'tor must signal an error
before calling close(). this is actually quite reasonable as such: once
the object is gone you can do no error checking, so discard on
destruction is the only clean option. of course this utterly breaks the
common non-error-checked pattern "open, write, go out of scope" - which
i consider no problem.
but i'm just being redundant with my previous posts here. joao didn't
try to dispute them any more, so assume they are the ultimate truth. ^^