如何在 Swift 3 中使用 CFDictionaryCreate？答案

【问题标题】：How to use CFDictionaryCreate in Swift 3?如何在 Swift 3 中使用 CFDictionaryCreate？
【发布时间】：2016-10-20 06:12:22
【问题描述】：

我想画一个带有裁剪矩形的属性字符串，我找到了一个用Objective-C写的函数，

CFDictionaryRef PINCHFrameAttributesCreateWithClippingRect(CGRect clippingRect, CGAffineTransform transform)
{
    CGPathRef clipPath = CGPathCreateWithRect(clippingRect, &transform);

    CFDictionaryRef options;

    CFStringRef keys[] = {kCTFramePathClippingPathAttributeName};
    CFTypeRef values[] = {clipPath};
    CFDictionaryRef clippingPathDict = CFDictionaryCreate(NULL,
                                                          (const void **)&keys, (const void **)&values,
                                                          sizeof(keys) / sizeof(keys[0]),
                                                          &kCFTypeDictionaryKeyCallBacks,
                                                          &kCFTypeDictionaryValueCallBacks);

    CFTypeRef clippingArrayValues[] = { clippingPathDict };
    CFArrayRef clippingPaths = CFArrayCreate(NULL, (const void **)clippingArrayValues, sizeof(clippingArrayValues) / sizeof(clippingArrayValues[0]), &kCFTypeArrayCallBacks);

    CFStringRef optionsKeys[] = {kCTFrameClippingPathsAttributeName};
    CFTypeRef optionsValues[] = {clippingPaths};
    options = CFDictionaryCreate(NULL, (const void **)&optionsKeys, (const void **)&optionsValues,
                                 sizeof(optionsKeys) / sizeof(optionsKeys[0]),
                                 &kCFTypeDictionaryKeyCallBacks,
                                 &kCFTypeDictionaryValueCallBacks);

    CFRelease(clippingPathDict);
    CFRelease(clippingPaths);
    CGPathRelease(clipPath);

    return options;
}

但是我在 Swift 3 中翻译失败，有人可以帮助我吗？

// 我尝试了以下代码，它编译并运行，但文本不做剪辑：

    let keys: [CFString] = [kCTFrameClippingPathsAttributeName]
    let values: [CFTypeRef] = [clipPath]

    let keysPointer = UnsafeMutablePointer<UnsafeRawPointer?>.allocate(capacity: keys.count)
    keysPointer.initialize(to: keys)

    let valuesPointer = UnsafeMutablePointer<UnsafeRawPointer?>.allocate(capacity: values.count)
    valuesPointer.initialize(to: values)

    let options = CFDictionaryCreate(kCFAllocatorDefault, keysPointer, valuesPointer, 1, nil, nil)

    let framesetter = CTFramesetterCreateWithAttributedString(attributedSring)
    let frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, attributedSring.length), rectPath.cgPath, options)
    CTFrameDraw(frame, context)

【问题讨论】：

标签： core-graphics swift3 cgcontext core-foundation

【解决方案1】：

构造一个 Swift 字典，然后将其转换为 CFDictionary。示例：

let d = [
        kCGImageSourceShouldAllowFloat as String : true as NSNumber,
        kCGImageSourceCreateThumbnailWithTransform as String : true as NSNumber,
        kCGImageSourceCreateThumbnailFromImageAlways as String : true as NSNumber,
        kCGImageSourceThumbnailMaxPixelSize as String : w as NSNumber
    ] as CFDictionary

【讨论】：