Hello,
I've been scratching my head trying to get a basic delegate/data
source Cocoa/AppKit program working and feel that I'm
misunderstanding something basic (I've included the code is at the
end).
I set a breakpoint within the if statement in the init method of
MyModel and see it called more than once. The second time the
debugger throws a EXC_BAD_ACCESS. This message goes away if I
comment out the two lines in stepAnimation that call the getBuffer
and getLength methods and then modify the buffer. All this makes me
think that somehow the instance of MyModel is being deallocated as
soon as the data source message returns, but before the data is
copied into the pointBuffer.
I created an NSView and NSObject in Interface Builder, assigning
the MyView subclass to the NSView object and MyModel to the
NSObject object. Then I connected the dataSource outlet on MyView
to th MyModel object.
What am I missing? How can I get the data from MyModel to be
viewable my MyView?
Sidenote: Ultimately I'm trying to plot a real-time frequency
spectrum. My plan is to pull in data over a CFMessagePort in the
model and have the view access it view the data source.
Help is much appreciated!
Chris
main.m
----------
int main(int argc, char *argv[]) {
// Launch Cocoa application
return NSApplicationMain(argc, (const char **) argv);
}
MyView.m:
----------
@implementation MyView
- (id)initWithFrame:(NSRect)frame {
self = [super initWithFrame:frame];
if (self) {
pointPath = [NSBezierPathbezierPath];
pointBuffer = malloc (sizeof(NSPoint) * 100);
[NSTimerscheduledTimerWithTimeInterval:0.1
target:self
selector:@selector(stepAnimation:)
userInfo:nil
repeats:YES];
}
return self;
}
- (void)drawRect:(NSRect)rect {
[pointPath removeAllPoints];
[pointPathappendBezierPathWithPoints:(NSPointArray)
pointBuffercount:100];
[pointPathstroke];
}
- (void)setDataSource:(id)inDataSource {
dataSource = inDataSource;
}
- (id)dataSource {
returndataSource;
}
- (void)stepAnimation:(NSTimer *)timer {
float*inBuffer;
int i, length;
// Fetch buffer pointer
inBuffer = [[self dataSource] getBuffer:self];
length = [[self dataSource] getLength:self];
// Copy to point buffer
for (i = 0; i < length; i++) {
pointBuffer[i].y = inBuffer[i];
pointBuffer[i].x = i;
}
// Mark display for painting
[selfsetNeedsDisplay:YES];
}
- (void)dealloc {
free(pointBuffer);
[super dealloc];
}
@end
MyView.h
----------
@interface MyView : NSView {
IBOutletid dataSource;
NSBezierPath *pointPath;
NSPoint *pointBuffer;
}
- (void)setDataSource:(id)inDataSource;
- (id)dataSource;
- (void)stepAnimation:(NSTimer *)timer;
@end
@interface NSObject(MyViewDataSource)
- (float *)getBuffer:(MyView *)view;
- (int)getLength:(MyView *)view;
@end
MyModel.m
----------
@implementationMyModel
- (id)init {
self= [superinit];
if (self) {
buffer = malloc (sizeof(float) * 100);
length = 100;
}
return self;
}
- (float *)getBuffer:(GraphView *)view {
returnbuffer;
}
- (int)getLength:(GraphView *)view {
returnlength;
}
- (void)dealloc {
free (buffer);
[super dealloc];
}
@end
MyModel.h
----------
@interface MyModel : NSObject {
float *buffer;
int length;
}
- (float *)getBuffer:(GraphView *)view;
- (int)getLength:(GraphView *)view;
@end
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