Convert PinchRecognizer Objective-C code to Swift

问题

I am trying to translate the Objective-C code to Swift, can someone help. I am stuck on one line.

Objective-C

-(void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer

{   
    if([pinchRecognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [pinchRecognizer scale];
    }

    if ([pinchRecognizer state] == UIGestureRecognizerStateBegan ||[pinchRecognizer state] == UIGestureRecognizerStateChanged)
    {
        ###I NEED TO CONVERT THIS LINE
        CGFloat currentScale = [[[pinchRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

        const CGFloat maxScale = 1.5;
        const CGFloat minScale = 1.0;

        CGFloat newScale = 1 -  (lastScale - [pinchRecognizer scale]);
        newScale = MIN(newScale, maxScale / currentScale);
        newScale = MAX(newScale, minScale / currentScale);
        thePageViewController.view.transform = CGAffineTransformScale(thePageViewController.view.transform, newScale, newScale);
        lastScale = [pinchRecognizer scale];  // Store the previous scale factor for the next pinch gesture call
    }
}

Swift

func pinchDetected(pinchRecognizer: UIPinchGestureRecognizer) {

    var lastScale = pinchRecognizer.scale

    if(pinchRecognizer.state == UIGestureRecognizerState.Began) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = pinchRecognizer.scale
    }

    if (pinchRecognizer.state == UIGestureRecognizerState.Began || pinchRecognizer.state == UIGestureRecognizerState.Changed)
    {

        ###HOW DO I CONVERT THIS LINE TO SWIFT?
        var currentScale: CGFloat = [[[pinchRecognizer.view].layer valueForKeyPath:@"transform.scale"] floatValue];

        let maxScale: CGFloat = 1.5;
        let minScale: CGFloat = 1.0;

        var newScale: CGFloat = 1 -  (lastScale - pinchRecognizer.scale)
        newScale = min(newScale, maxScale / currentScale);
        newScale = max(newScale, minScale / currentScale);
        self.view.transform = CGAffineTransformScale(self.view.transform, newScale, newScale);
        lastScale = pinchRecognizer.scale  // Store the previous scale factor for the next pinch gesture call
    }

}

回答1:

The Line you mentioned to convert can be done like this. This worked for me.

var curScale = pinchRecognizer.view!.layer.valueForKeyPath("transform.scale")!.floatValue

来源：https://stackoverflow.com/questions/29787541/convert-pinchrecognizer-objective-c-code-to-swift