Re: copyWithZone: -- selector not recognized
Re: copyWithZone: -- selector not recognized
- Subject: Re: copyWithZone: -- selector not recognized
- From: Cameron Hayne <email@hidden>
- Date: Tue, 4 Jun 2002 20:37:12 -0400
Matt Neuburg <email@hidden> wrote:
I have a table view and in : tableView:objectValueForTableColumn:row
I'm trying to return an element
like this:
return itemObj ; //where itemObj is an RSItemObject
Can anyone tell me what am I doing wrong because I'm receiving the
following error message :
>> [RSItemObject copyWithZone : ] : selector not recognized
and I really don't know what might be wrong !
The message tells you exactly what's wrong; you're returning something
that
the table view has no way of knowing how to make a copy of.
This is a documentation issue.
The problem is that the error message is referring to something which
happens behind the scenes and is not directly related to anything in the
original poster's code. He didn't invoke 'copyWithZone' - so he is
justifiably confused when he gets the error message. One way to
alleviate this difficulty would be to have a searchable list of error
messages together with explanations of common causes for the errors.
Anyhow, you
probably wanted to return something like an NSString; how is a table
going
to display an itemObj?
This is the real issue. And again it is a documentation issue. As a
Cocoa newbie, I have never used an NSTableView and when (sparked by this
question) I read the protocol description for
tableView:objectValueForTableColumn:row, I didn't see any mention of the
crucial fact that the object returned must have an NSFormatter method
for the table to use when displaying it. The "Using A Table Data Source"
concept page says:
"The NSTableView treats objects provided by its data source as values to
be displayed in NSCell objects. If these objects aren't of common value
classessuch as NSString, NSNumber, and so onyou'll need to create a
custom NSFormatter to display them."
This paragraph should appear in the protocol description.
... Cameron
--
Cameron Hayne (email@hidden)
Hayne of Tintagel
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