Re: Annoying Superclass Implemenation Warning
Re: Annoying Superclass Implemenation Warning
- Subject: Re: Annoying Superclass Implemenation Warning
- From: Steve Christensen <email@hidden>
- Date: Mon, 21 Jan 2008 15:52:46 -0800
Chris Hanson educated me on this topic awhile back when I was trying
to make an common Obj-C class part of a static library which was then
linked into multiple plugins. To quote him:
You have thus far been able to get away with using a static library
for this approach only because you haven't been using Objective-C.
Once you start using Objective-C, you will not be able to use a
static library, because while C++ classes are not objects and have
little associated runtime data structure associated with them,
Objective-C classes are objects and are associated with substantial
runtime data structures. You cannot have the same class registered
in the same runtime multiple times, which is what would happen if
you had two plug-ins link your static library and get loaded into
the same application.
You're basically in the same boat. When your plugin #1 loads, the
common class is registered with the Obj-C runtime. When plugin #2
loads, you get the warning message that says you've already
registered the class once. Another build phase won't help you out.
What Mike had suggested doing is to create a target that builds a
framework containing the common class. Your plugin targets are then
dependent on that target and also link against the framework it
builds. When you install, your plugins go in the prefs panes folder
and the custom framework goes in the frameworks folder. Then when
plugin #1 loads, it forces the framework to load and register the
common class. When plugin #2 loads, the class has already been
registered, once, by the framework so there's no second attempt at
registration.
steve
On Jan 21, 2008, at 3:17 PM, Ben Einstein wrote:
I understand why the message is occurring, I'm just not sure the
appropriate way to get rid of it. The plugin build fails if I
remove the superclass from the plugin target and place it in the
main app target (can't find class symbol). Do I need to add another
build phase?
Ben
On Jan 21, 2008, at 6:03 PM, Mike Abdullah wrote:
Well the message means exactly what it says: You've implemented
the class in multiple plugins. Thus, the ObjC runtime cannot be
sure which implementation to use. I would suggest you place the
superclass within the main framework/application that the plugins
are built against.
Mike.
On 21 Jan 2008, at 22:20, Ben Einstein wrote:
Hi All:
I have 15 or so preference panes implemented in my own preference
pane viewer. Because the app started with only 2 or 3 panes,
every pane had 6 or 7 identical methods. I had some free time
this weekend and made a superclass to handle this dull pane
stuff. I now get this annoying message in the console every time
a user switches between panes:
objc[5347]: Class <SuperclassName> is implemented in both /Path/
To/Preference/Pane1/PaneName1 and /Path/To/Preference/Pane2/
PaneName2. Using implementation from /Path/To/Preference/Pane1/
PaneName1.
Any ideas to get the console to shut up? Not sure what I'm doing
wrong.
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