Re: Strange property/synthesized accessor behaviour
Re: Strange property/synthesized accessor behaviour
- Subject: Re: Strange property/synthesized accessor behaviour
- From: "Stephen J. Butler" <email@hidden>
- Date: Sun, 10 Apr 2011 03:00:28 -0500
On Sat, Apr 9, 2011 at 9:52 AM, Philipp Leusmann <email@hidden> wrote:
> Who can explain this behavior to me? Why is oWidth != object.mWidth ? How can that happen?
It's an artifact of how Objective-C searches for selector
implementations. You're calling @selector(width) on an "id", and of
course "id" doesn't implement @selector(width).
So what Objective-C does is search for the first implementation of
@selector(width) that it finds. My guess is it finds the one in AppKit
first (greping the frameworks):
NSTableColumn.h:- (CGFloat)width;
Then when the compiler sets up the call site it does it expecting a
CGFloat return and that is handled differently than an integer. So the
call site and the implementation of how your width is done disagree
and you get some strange heisenvalue back.
When you cast the variable to "Result*", Objective-C now knows to use
YOUR implementation of @selector(width) and it sets up the call site
properly.
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