在SQLite中保存UIBezierPath

Question

我正在使用 UIBezierPath 在视图上徒手绘制注释。我想将它保存在 SQLite 中，以便在用户打开该视图时在该视图上绘制。有没有办法在 SQLite 中保存 UIBezierPath，这样我就可以随时使用它来绘制视图。

Answer 1

您可以将其序列化为数据（以 NSData 实例的形式），因为 UIBezierPath 符合 NSCoding （即

NSData * data = [NSData archivedDataWithRootObject:yourPath]

另一种选择可能是与 SVG 相互转换并保存。

Answer 2

您可以保存

UIBezierPath

的所有控制点，而不是直接保存路径。

Answer 3

您可以通过定义路径模型并使用 Codable 来序列化/反序列化

UIBezierPath

。虽然将

lineWidth

或

lineCapStyle

等属性设置为

Codable

很简单，但路径元素的代码（存储在

UIBezierPath.cgPath

中）则更为复杂。然而，这是一个起点：

enum PathElement: Codable, Equatable {
    case moveToPoint(CGPoint)
    case addLineToPoint(CGPoint)
    case addQuadCurveToPoint(controlPoint: CGPoint, endPoint: CGPoint)
    case addCurveToPoint(controlPoint1: CGPoint, controlPoint2: CGPoint, endPoint: CGPoint)
    case closeSubpath
}

extension CGPath {
    static func pathFromPathElements(_ pathElements: [PathElement]) -> CGPath {
        let path = CGMutablePath()

        for pathElement in pathElements {
            switch pathElement {
            case .moveToPoint(let point):
                path.move(to: point)
            case .addLineToPoint(let point):
                path.addLine(to: point)
            case .addQuadCurveToPoint(let controlPoint, let endPoint):
                path.addQuadCurve(to: endPoint, control: controlPoint)
            case .addCurveToPoint(let controlPoint1, let controlPoint2, let endPoint):
                path.addCurve(to: endPoint, control1: controlPoint1, control2: controlPoint2)
            case .closeSubpath:
                path.closeSubpath()
            }
        }
        return path
    }

    func pathElements() -> [PathElement] {
        var result = [PathElement]()

        applyWithBlock { elementPointer in
            let element = elementPointer.pointee
            switch element.type {
            case .moveToPoint:
                let points = Array(UnsafeBufferPointer(start: element.points, count: 1))
                let el = PathElement.moveToPoint(points[0])
                result.append(el)
            case .addLineToPoint:
                let points = Array(UnsafeBufferPointer(start: element.points, count: 1))
                let el = PathElement.addLineToPoint(points[0])
                result.append(el)
            case .addQuadCurveToPoint:
                let points = Array(UnsafeBufferPointer(start: element.points, count: 2))
                let el = PathElement.addQuadCurveToPoint(
                    controlPoint: points[0], endPoint: points[1])
                result.append(el)
            case .addCurveToPoint:
                let points = Array(UnsafeBufferPointer(start: element.points, count: 3))
                let el = PathElement.addCurveToPoint(
                    controlPoint1: points[0], controlPoint2: points[1], endPoint: points[2])
                result.append(el)
            case .closeSubpath:
                result.append(.closeSubpath)
            @unknown default:
                fatalError()
            }
        }

        return result
    }
}