xcode CGMutablePath.addArc 在 Swift 3 中不起作用？
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CGMutablePath.addArc not working in Swift 3?
提问by GoldenJoe
In Xcode 8 beta 6, some of the functions to add a path changed, including those that add an arc:
在 Xcode 8 beta 6 中，一些添加路径的函数发生了变化，包括添加弧的函数：
func addArc(center: CGPoint, radius: CGFloat, startAngle: CGFloat, endAngle: CGFloat, clockwise: Bool, transform: CGAffineTransform = default)
Beyond a definition of the function, there is no documentation on Apple's site. I've been unable to get an actual arc from this function, and have been relying on a second version that uses tangents. Can anyone provide a working sample? Could it just be bugged?
除了函数的定义之外，Apple 的网站上没有任何文档。我一直无法从这个函数中得到实际的弧线，一直依赖于使用切线的第二个版本。任何人都可以提供工作样本吗？可能只是被窃听了吗？
Here is a function that is broken by the change:
这是一个被更改破坏的函数：
public class func createHorizontalArcPath(_ startPoint:CGPoint, width:CGFloat, arcHeight:CGFloat, closed:Bool = false) -> CGMutablePath
{
// http://www.raywenderlich.com/33193/core-graphics-tutorial-arcs-and-paths
let arcRect = CGRect(x: startPoint.x, y: startPoint.y-arcHeight, width: width, height: arcHeight)
let arcRadius = (arcRect.size.height/2) + (pow(arcRect.size.width, 2) / (8*arcRect.size.height));
let arcCenter = CGPoint(x: arcRect.origin.x + arcRect.size.width/2, y: arcRect.origin.y + arcRadius);
let angle = acos(arcRect.size.width / (2*arcRadius));
let startAngle = CGFloat(M_PI)+angle // (180 degrees + angle)
let endAngle = CGFloat(M_PI*2)-angle // (360 degrees - angle)
let path = CGMutablePath();
path.addArc(center: arcCenter, radius: arcRadius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
if(closed == true)
{path.addLine(to: startPoint)}
return path;
}
回答by Martin R
Your Swift code is based on the Objective-C code from http://www.raywenderlich.com/33193/core-graphics-tutorial-arcs-and-paths, where the arc path is created as
您的 Swift 代码基于来自http://www.raywenderlich.com/33193/core-graphics-tutorial-arcs-and-paths的 Objective-C 代码，其中弧路径创建为
CGPathAddArc(path, NULL, arcCenter.x, arcCenter.y, arcRadius,
startAngle, endAngle, 0);
In particular, 0is passed as argument to the last parameter bool clockwise. That should be translated to falsein Swift, not true:
特别是，0作为参数传递给最后一个参数bool clockwise。这应该false在 Swift 中转换为，而不是true：
path.addArc(center: arcCenter, radius: arcRadius,
startAngle: startAngle, endAngle: endAngle, clockwise: false)
