保存Coregraphics绘图操作?

我有什么办法可以做到:

@实施myview

- (void)drawRect:(CGRect)rect
{
   // Get the thing I'm supposed to draw (CGImageRef, pattern, etc.) and draw it
   // i.e. not real code
   CGContextDrawWhatever(self.objectThatHoldsDrawing.drawing);
}