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I’m trying to subclass General/NSCell to get functionality similar to that of the cells in the Property List Editor utility, where most of the time the cell is a text field, but can also turn into an General/NSPopUpButton(Cell). I’ve almost got it working, but it doesn’t quite work properly.

Here’s the code:

@interface General/NSCellSubclass : General/NSTextFieldCell { BOOL displayPopUpButton; General/NSPopUpButton *control; }

@implementation General/NSCellSubclass


This works for the most part, but if you try it, you’ll notice that the control will do some strange drawing things when it’s trying to act as a pop-up button, such as draw over itself, and not go away when it’s told to start acting like a text field again.

Any help would be great :-D

– General/KentSutherland

The reason for the drawing problems is that you’re creating a new General/NSPopUpButton every time you draw (and losing your reference to the old one), so you’re creating stacks of popup buttons drawingon top of each other. More fundamentally, using a view within a cell is a bad idea as some classes (like table and outline views) reuse cells to draw in several different locations; I’d advise just deciding whether you want a cell to be a text field or popup button cell and creating the appropriate cell type at run time. Alternatively, you can use an General/NSProxy subclass to forward messages to an appropriate cell instance; the General/ForwardInvocation sample project /Developer/Examples/Foundation demonstrates how to set this up. – Bo

If I were going to create a new cell at runtime each time, wouldn’t that slow things down a lot? And even if I were going to do that, how does one make a new cell and have the outline view display it?

To have individual rows use different cells in a table or outline view, you have to subclass General/NSTableColumn and override the method -dataCellForRow:. Since you’re subclassing the column anyway,you could have it create one cell instance for each type of cell (i.e. one General/NSTextFieldCell and one General/NSPopUpButtonCell) at initialization time and then have it return the appropriate instance for each row. That way you won’t be creating a bunch of cells, just 2. – Bo

Subclassing General/NSTableColumn and dataCellForRow worked great, thanks :) – General/KentSutherland