Swift xcode错误：无法推断出＆＃39; shape＆＃39;和错误类型中找不到枚举案例

Question

我试图在xcode中创建一个绘图方法，以便在UIView中绘制不同的形状。此应用程序的目的是将绘图附加到保存在表格中的行（如果需要，我将发布表格代码，但我不认为这个错误是必要的）。

错误的屏幕截图：

import UIKit



/*

    This program is for Xcode 6.3 and Swift 1.2

*/





class CanvasView: UIView {

    enum ShapeType: String

    {

        case Line = "Line"

        case Ellipse = "Ellipse"

        case Rectangle = "Rectangle"

        case FilledEllipse = "Filled Ellipse"

        case FilledRectangle = "Filled Rectangle"

        case Scribble = "Scribble"

    }



    var shape: ShapeType = .Line

    var color: UIColor = UIColor.blueColor()

    var first :CGPoint = CGPointZero

    var last  :CGPoint = CGPointZero

    var points: [CGPoint] = []



    // Only override drawRect: if you perform custom drawing.

    // An empty implementation adversely affects performance during animation.

    override func drawRect(rect: CGRect) {

        // Drawing code

        let context = UIGraphicsGetCurrentContext()

        CGContextSetStrokeColorWithColor(context, color.CGColor)

        CGContextSetFillColorWithColor(context, color.CGColor)



        let rect = CGRect(x: first.x, y: first.y, width: last.x - first.x, height: last.y - first.y)

        switch shape {

        case .Line:

            CGContextMoveToPoint(context, first.x, first.y)

            CGContextAddLineToPoint(context, last.x, last.y)

            CGContextStrokePath(context)

        case .Ellipse:

            CGContextStrokeEllipseInRect(context, rect)

        case .Rectangle:

            CGContextStrokeRect(context, rect)

        case .FilledEllipse:

            CGContextFillEllipseInRect(context, rect)

        case .FilledRectangle:

            CGContextFillRect(context, rect)

        case .Scribble:

            CGContextMoveToPoint(context, first.x, first.y)

            for p in points {

                CGContextAddLineToPoint(context, p.x, p.y)

            }

            CGContextStrokePath(context)

        }

    }



    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

        if let touch = touches.first {

            first = touch.locationInView(self)

            last = first

            points.removeAll(keepCapacity: true)

            if shape == .Scribble {

                points.append(first)

            }

            setNeedsDisplay()

        }

    }



    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

        if let touch = touches.first {

            last = touch.locationInView(self)

            if shape == .Scribble {

                points.append(last)

            }

            setNeedsDisplay()

        }

    }



    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {

        if let touch = touches.first {

            last = touch.locationInView(self)

            if shape == .Scribble {

                points.append(last)

            }

            setNeedsDisplay()

        }

    }



    override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?) {

    }



}