Newbie Q on posing

FROM : delanoy
DATE : Sat Jul 22 19:36:26 2006

Hello all,

I created a subclass of NSTextView (called GGTextView) that differs
from its superclass only by the implementation of the
-pageFooter: method, and I'm trying to "replace
NSTextView with GGTextView everywhere" in the source code
for TextEdit, so that when the new version of TextEdit runs
only the new "-pageFooter:" method is called.

So I replaced NSTextView with GGTextView in the .h and .m files where
it was possible, and seemed reasonable, to do so.
(In particular :

    1)      replace every [[NSTextView alloc] init] with [[GGTextView
alloc] init]
    2)    replace every method returning an NSTextView with one
    returning an GGTextView.
)


  Having done this, I get a project that builds without "incompatible
types" warnings
and runs fine, but unfortunately does not do what I want in some cases :
sometimes
a text view is of class NSTextView instead of GGTextView. My guess is that
this problem
comes from the only case where I could not apply rule 2), namely the method

  - (NSTextView *)firstTextView {
    return [[self layoutManager] firstTextView];
}

  in Document.m. The stumbling block here is that, one way or another,
one has to "transform an NSTextView into a GGTextView." I tried to replace
the
code above with the following :

- (GGTextView *)firstTextView {
    [GGTextView poseAsClass: [NSTextView class]];
    return [[self layoutManager] firstTextView];
}


This produces a warning and a crash at runtime. What is the right way to
use posing
in this situation ? Should I leave all those NSTextViews alone and just
add the line

  [GGTextView poseAsClass: [NSTextView class]];

in a piece of code that gets called early ?

                                                                    Ewan