Re: NSTableColumn not usable with binder of class NSTextValueBinder?
Re: NSTableColumn not usable with binder of class NSTextValueBinder?
- Subject: Re: NSTableColumn not usable with binder of class NSTextValueBinder?
- From: Ron Lue-Sang <email@hidden>
- Date: Tue, 26 Aug 2008 23:34:33 -0700
Woah.
If you really want to use a custom cell, you're gonna want a custom
column as well. The bindings for the tableColumn come from the
tableColumn's dataCell's available bindings. Yea, as you've found,
NSActionCell has a value binding, not plain old NSCell.
But of course, nothing's as simple as it seems to be. It's not like
the tableColumn asks for its dataCell's exposedBindings and then just
re-expose those bindings. It's just not that simple.
Don't ask. Feel free to file a bug tho.
Developers, however, are free to do this in their NSTableColumn
subclasses. So you're custom cell implements and exports an extra
binding. The trick is - how do you go from your cell's binding name to
a setter? You need to implement NSTableColumn's dataCellForRow: to
return a fully set up dataCell - with all the values specified by the
binding "put" into the datacell. Doing this is easy enough if you use
the same name for the cell's binding as you would for the setter.
The reason you're seeing the exception is that you've switched out
the cell out from under the tablecolumn before the binding is set up.
When the tableColumn is issued the bind:… command, it falls back to
the plain old KVB implementation which assumes NSTableColumn
implements setValue: (KVC compliant for "value" key).
Does any of this make sense?
Possibly, you've already solved this some other way, but hopefully
I've cleared up a couple of things.
On Aug 20, 2008, at 10:33 PM, Dave Dribin wrote:
On Aug 20, 2008, at 3:35 AM, Ken Ferry wrote:
FYI, you should avoid using direct subclasses of NSCell in controls
on
Leopard and previous.
Well, that settles that, then. ;)
It's somewhat unfortunate, but there are many cases where messages
need to flow from a cell up to a view. If your cell isn't an action
cell, that message flow won't work. It's usually fine as long as
your
cell is purely stamped out drawing. If your cell has more
complicated
interactions with the user, like use of a field editor or rollovers
or
what have you, you're liable to see problems with non-action cells.
This cell is just drawing, but given the bindings issue and the
advice above, it looks like staying away from NSCell is a good idea,
ATM.
I suspect the problem here is that NSCell and NSActionCell don't have
a value binding! Check the Cocoa bindings reference.
Well, the Cocoa bindings reference does not have an entry for either
NSCell or NSActionCell. For the next best thing, I printed out the
return value of -exposedBindings for both. For NSCell, we've got
these bindings:
Exposed bindings: (
editable,
enabled,
font,
fontBold,
fontFamilyName,
fontItalic,
fontName,
fontSize
)
And for NSActionCell, we've got these:
Exposed bindings: (
editable,
enabled,
font,
fontBold,
fontFamilyName,
fontItalic,
fontName,
fontSize,
value
)
Indeed, NSActionCell has a "value" binding while NSCell does not.
The information about how the bindings need to be hooked up may be
determined at design time in IB. If IB thinks you have a text cell,
you might get a binding set up in a way appropriate for a text cell.
In any case, this 'binder' thing should have a bug too, if you
please.
The NSTextValueBinder error message is a bug? Or the fact that
NSCell does not have a "value" binding? Or both? ;)
If you want to go the bindings route, you could implement a value
binding on your cell subclass by overriding -bind:toObject:
withKeyPath:options: and then bind at runtime. That'd probably do
the
trick.
I tried this, and it does not work. In fact -
bind:toObject:withKeyPath:options: never gets called in my NSCell
subclass. I even called [self exposeBinding:@"value"] in
+initialize, and bind:toObject:... still does not get called. Is
this a different bug? It seems like I should be able to add
bindings to an NSCell subclass in this way.
In any case, I'm back to subclassing NSActionCell as the way to get
this working.
-Dave
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RONZILLA
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