I'm working through an experiment, and I think I'm close, but I'm not
quite lining things up. I've Googled old list entries and haven't
found an answer yet.
In a nutshell, I want to bind the return value of a method in my main
window's controller to an input on Quartz Composer composition.
Ultimately, the demo will use QC to render the audio level of a
QuickTime movie, which will satisfy my curiosity about using QC as a
nifty way to render application data.
The trick is getting the bindings worked out. I've been working from
the Quartz Composer Programming Guide and the Cocoa Bindings
Programming Topics docs, as well as various tech notes and blogs I've
found by way of Google.
The first thing I wanted to convince myself of is that it would work
to bind a method's return value to a GUI component (this is implicit
in KVC looking for methods or variables that match the bound key; I
just wanted to see it for myself). I created an Object Controller,
connected it to MyController in IB, and used IB to bind an NSTextField
to Object Controller.selection.movieLevel. Works fine, returns my
current dummy value.
So next, I started working on the QC side of the equation. I added a
QCView and a QCPatchController, loaded the the composition into the
controller, and connected the view to the controller with IB.
Simulating this from IB worked: I saw my composition in the window.
Now, here's what I think is the hard part: binding the method in
MyController to the input in the QC composition. It occurs to me that
IB doesn't know about my controller's method name, or about the inputs
to the composition. If I understand the situation, this means I need
to establish the binding programmatically.
To do that, I add variables for the NSObjectController (still
connected to MyController from before), and the QCPatchController to
MyController.h:
IBOutlet id patchController;
IBOutlet NSObjectController *objController;
Note that I used a plain id because QCPatchController doesn't have a
public header. OK, so I connected MyController to these respective
objects, so now I think I have what I need for MyController to
programmatically bind its own movieLevel method (by way of the
objController) to the input on the QC composition. So I try the
following in awakeFromNib:
- (void)awakeFromNib {
NSLog(@"awakeFromNib!");
[objController bind:@"selection.movieLevel"
toObject:patchController
withKeyPath:@"patch.MyText.value"
options:nil];
NSLog (@"Called bind");
}
And... it doesn't work. The runtime tells me that something here
isn't KVC compliant:
2008-01-16 14:06:19.797 QCLevelMeterExperiment1[2244:10b] awakeFromNib!
2008-01-16 14:06:19.819 QCLevelMeterExperiment1[2244:10b] An uncaught
exception was raised
2008-01-16 14:06:19.821 QCLevelMeterExperiment1[2244:10b]
[<NSObjectController 0x18dd60> setValue:forUndefinedKey:]: this class
is not key value coding-compliant for the key selection.movieLevel.
So, that's the situation. I can't tell if I'm on the right track and
just haven't provided appropriate paths for the binding, or if I'm
really going off in the wrong direction.
Thanks in advance for any advice. If it turns out that someone's
already written this up or blogged it, then apologies for not managing
to find it.
--Chris
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