Animate CGContextFillRect - iphone

Question

I have a progress view that I'm trying to animate the change in progress. How do you go about doing that? Below is the code to draw the progress.
Thanks in advance
- (void)drawRect:(CGRect)rect {
// Drawing code.
CGContextRef context = UIGraphicsGetCurrentContext();
// draw the background
CGContextSaveGState(context);
UIBezierPath *outerPath = [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:0];
[outerPath addClip];
CGPoint backgroundStartPoint = CGPointMake(0.0f, 0.0f);
CGPoint backgroundEndPoint = CGPointMake(0.0f, CGRectGetHeight(rect));
CGContextDrawLinearGradient(context, _backgroundGradient, backgroundStartPoint, backgroundEndPoint, 0);
CGContextRestoreGState(context);
// draw the progress
CGContextSaveGState(context);
UIBezierPath *innerPath = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, 1.0f, 1.0f) cornerRadius: 0];
[innerPath addClip];
[_glossTintColor setFill];
CGRect progressRect = CGRectMake(0, 0, CGRectGetWidth(rect)*_progress, CGRectGetHeight(rect));
CGContextFillRect(context, progressRect);
CGContextRestoreGState(context);
}

Answer 1

Whenever the progress changes, trigger a redraw using [view setNeedsDisplay];
See the UIView reference on setNeedsDisplay.
For example, lets say that custom view you have created has a property called progress, the instance variable is called _progress. Lets also suppose that property gets updated by some event/timer/additional thread.
- (void)setProgress:(float)progress
{
_progress = progress;
[self setNeedsDisplay];
}
That overrides the original setter and adds the functionality mentioned above.