ios – 在Swift中调用CGPatternCreate

CGPatternRef pattern = CGPatternCreate(NULL,
                                       rect,
                                       CGAffineTransformIdentity,
                                       24,
                                       24,
                                       kCGPatternTilingConstantSpacing,
                                       true,
                                       &callbacks);

我的代码：

let callbacks : CGPatternCallbacks = CGPatternCallbacks(version: 0)

    let pattern : CGPatternRef = CGPatternCreate(nil,
        rect,
        CGAffineTransformIdentity,
        24,
        24,
        kCGPatternTilingConstantSpacing,
        true,
        callbacks)

但是我收到了一条错误消息：

‘CGPatternCallbacks’ is not convertible to ‘CConstPointer’

有没有示例代码？谢谢

var callbacks : CGPatternCallbacks = CGPatternCallbacks(version: 0)

var pattern = CGPatternCreate(nil,
    rect,
    CGAffineTransformIdentity,
    24,
    24,
    kCGPatternTilingConstantSpacing,
    true,
    &callbacks)