Description: When I conclude project 9 days three I found some problems.

 We create a checkerBoard with four rows and four columns,then if the sum of the row number and column number can be perfectly divided by 2,we draw a rectangle.

              let startX=columnsize*CGFloat(column)
              let startY=rowsize*CGFloat(row)

              let rect=CGRect(x: startX, y: startY, width: columnsize, height: rowsize)

             mypath.addRect(rect)

But I have a new ideal,what should I do if I want draw a circle? So,I try to do that by myself,and the following code is what I did,unfortunately,it doesn't work well:

                let startX=columnsize*CGFloat(column)
                let startY=rowsize*CGFloat(row)

                //let rect=CGRect(x: startX, y: startY, width: columnsize, height: rowsize)

               // mypath.addRect(rect)

                mypath.addArc(center: CGPoint(x:startX+columnsize/2, y: startY+rowsize/2), radius: rowsize/4, startAngle: .degrees(0), endAngle: .degrees(360), clockwise: true)

The problem is that I just see only one circle on my screen,but it should be more actually.I guess the key is "mypath.addArc"just performs once,I think about it a lot and can't find a solution to solve it.

I am so sorry for taking your time to turn to you,but I do have no idea about it,so ,thanks again,sincerely.