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I started working on an NSSlider subclass (let’s call it XSlider) that draws its background in a special way (via a matching NSSliderCell subclass called XSliderCell). Got that working, so far, so good. I can drag out an NSSlider in IB, change its class to XSlider, and there I go. Along the way, I found that overriding +cellClass wasn’t working for things loaded from IB, so I programmatically set the cell in -initWithCoder:.

When I started playing with the slider in IB though (changing between regualar/small/mini, showing ticks or not, etc), I got weirdness when when those objects were loaded from the nib; It turns out that most of those parameters are actually stored in the NSSliderCell instance in the nib file (rather than in the XSliderCell instance), so when I manually set a new XSliderCell instance in initWithCoder:, most of that info is lost, resulting in weird drawing.

I can’t find any way to specify the cell class for my XSlider within IB, so I figured I would build a palette. I made a palette containing XSlider and XSliderCell, put both XSlider and XSliderCell into my palette.table, put an XSlider into my XSliderPalette.nib (by dragging out an NSSlider and changing its class). Since my subclass doesn’t allow any customization at this level beyond what NSSlider provies, I made use of the standard NSSlider inspector controls by returning @”IBSliderInspector” from -[XSlider inspectorClassName].

The palette compiled and loaded into IB fine, except that the sliders in the palette looked like normal NSSliders, not like my fancy XSliders (but I put that on the back burner for the moment). I rebuilt my interface using XSliders dragged in from the new palette, rebuilt my app, and… I still have the same problem as before!

The reason is that even the XSliders I pull in from the new palette were, themselves, originally NSSliders from the normal palette, and are therefore still making use of NSSliderCell instead of XSliderCell! This is, of course, also why the sliders in my new palette look like normal sliders: they are being drawn by NSSliderCell.

The solution, it turns out, is to create the palette nib in a slightly different way: Instead of dragging an NSSlider into the view, I drag in a CustomView and then set its class to XSlider. Doing so ensures that a new XSlider is created, which will use its +cellClass method to create an XSliderCell. Now, I can drag in XSliders from my palette, reconfigure them with the normal slider inspector panels, and everything looks and works as it should both in IB and in my project.

This posting started out as a plea for help, but about halfway through, just writing it down helped me figure out the solution myself. Thanks, me! I figured I may as well post it here anyway, to document it for posterity.

// JackNutting

Sounds like a great solution to a (relatively) common problem, but I have one question. If you rebuilt your palette using an early version of your palette (bootstrapping, I guess), doesn’t that mean that your palette requires your palette to load? Will it still work if you remove all of the versions of the palette from IB (using the Preferences window)? –JediKnil

Actually, it works fine. The nib file for my palette doesn’t really know about XSlider and XSliderCell, other than that they exist. That’s what dragging out a custom view gives you, the ability to put arbitrary classes into your GUI. As long as they’re there at runtime in the compiled app, that’s all you need. Incidentally, when I look at the nib for my palette, I don’t see my slider the way it really looks, I just see the dark gray custom-view box. When the compiled palette is loaded in IB however, the slider appears as it should.

// JackNutting