写字符串会给我错误，写图像不会

I have this code:

我有这段代码:

            let image = UIImage(data: downloadedImage!)


            let convertImage = UIImagePNGRepresentation(image!)
            let pathUIDImage = self.getDocumentsDirectory().appendingPathComponent(playersUID + "Image")
            try? convertImage!.write(to: pathUIDImage) //working


            let playersUIDImageVersion = "1"
            var pathUIDImageVersion = self.getDocumentsDirectory().appendingPathComponent(playersUID + "ImageVersion")
            try? playersUIDImageVersion.write(to: pathUIDImageVersion) //error
            let i