Quartz2D: How to draw an arc of a circle?

Question

I would like to draw an arc of a circle like in this sketch:

The angle of the arc should be variable and it should be colored with a gradient (eg starting with red and going to green). How do you do this in Quartz2D?

Thanks for your answers! Stefan

Answer 1

我认为此页面具有弧形部分，而此部分处理渐变的绘制。