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Я хочу нарисовать приписываемую строку с обрезкой rect, и я нашел функцию, написанную на Objective-C,

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

    CFDictionaryRef options;

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

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

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

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

    return options;
}
  

Но мне не удалось перевести его в Swift 3, кто-нибудь может мне помочь?

// Я пробовал нижеприведенные коды, он компилируется и запускается, но текст не выполняет клип:

     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)
  

Создайте словарь Swift и затем приведите его к CFDictionary . Пример:

 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
  

Более подробная информация здесь:https://bugs.swift.org/browse/SR-2388