相关疑难解决方法(0)

我正在将NSView移植到Swift,我需要使用Quartz CGContextAddPath.

import Cocoa

class MYView: NSView {

    init(frame: NSRect) {
        super.init(frame: frame)
    }

    override func drawRect(dirtyRect: NSRect) {
        super.drawRect(dirtyRect)


        NSColor .redColor() .set()
        NSRectFill(self.bounds)
        var p :CGMutablePathRef = CGPathCreateMutable()
        var ctx =  NSGraphicsContext.currentContext().graphicsPort()
        CGContextAddPath(ctx, p) // compiler rejects this line

    }

}

你怎么理解这个错误信息？

Cannot convert the expression's type 'Void' to type 'CGContext!'

CGContextAddPath的Swift签名是:

func CGContextAddPath(context: CGContext!, path: CGPath!)

我的错误是什么？

我用这个时:

let context = UnsafePointer<CGContext>(ctx).memory

我现在有一个运行时错误:

Jun 3 15:57:13 xxx.x SwiftTest[57092] <Error>: CGContextAddPath: invalid context 0x7fff73bd0060. This is a serious error. …

我正在尝试将此objc代码转换为swift:

CGContextRef contextRef = CGBitmapContextCreate(NULL,
                                                proposedRect.size.width,
                                                proposedRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                0,
                                                colorSpaceRef,
                                                (CGBitmapInfo)kCGImageAlphaPremultipliedFirst);
NSGraphicsContext *context = [NSGraphicsContext graphicsContextWithGraphicsPort:contextRef flipped:NO];

到目前为止,我最终得到了这个:

var bitmapContext: CGContext = CGBitmapContextCreate(data, UInt(proposedRect.width), UInt(proposedRect.height), CGImageGetBitsPerComponent(image), 0, colorSpace, CGBitmapInfo(CGImageAlphaInfo.PremultipliedFirst.toRaw()))
let context = NSGraphicsContext(graphicsPort: bitmapContext, flipped: false)

问题是,CGBitmapContextCreate收益CGContext类型和NSGraphicsContext初始化参数graphicsPort的CMutableVoidPointer类型.那我怎么转换CGContext成CMutableVoidPointer？

相关的反向类型转换在这里找到,但它没有提供太多帮助 如何将swpa中的COpaquePointer转换为某种类型(特别是CGContext？)