To maximize and display the UIImageView image from above while maintaining aspect

I'm sorry it's a utility method, but you can do it if you insert a code that cuts out the image you want to set in the UIImageView as follows:

Clip and set the image specified in //image to fit in toSetImgView
/// -parameter image:image you want to set in UIImageView
/// -parameter toSetImgView—Instance of UIImageView where you want to set the image
funcsetReservedImageToUIImageView (image: UIImage, toSetImgView: UIImageView)
{
    letcImg: CGIimage?=image.cgImage;
    if(cImg==nil)
    {
        return
    }

    // Cut out the image so that it can be displayed well
    let imgRef:CGImage?=cImg?.cropping(to:CGRect(x:0,y:0,width:image.size.width,height:toSetImgView.frame.size.height*image.size.width/toSetImgView.frame.size.width))
    if(imgRef==nil)
    {
        return
    }

    let newImg=UIImage(cgImage:imgRef!, scale:image.scale, orientation:image.imageOrientation)

    toSetImgView.image=newImg
}

Actually, I wanted to inherit UIImageView and do it on KVO, but Swift was unfamiliar and didn't work.(I think it's a poor code for Swift.)
If you receive notification that the image property has been changed in KVO, you will be able to make it smarter by calling the above process there.