swift 4 UITableView页脚,绝对底部

let customView = UIView(frame: CGRect(x: 0, y: self.view.bounds.height - 50, width: self.view.bounds.width, height: 50))
            customView.backgroundColor = UIColor.red

            commentText = UITextField(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width - 50, height: 50))
            commentText.backgroundColor = UIColor.white
            commentText.layer.borderColor = UIColor.gray.cgColor
            commentText.layer.borderWidth = 1
            commentText.borderStyle = .roundedRect
            commentText.placeholder = "Enter Comment"

            let submitButton = UIButton(frame: CGRect(x: self.tableView.bounds.width - 50, y: 0, width: 50, height: 50))
            submitButton.setTitle("Go", for: .normal)
            submitButton.backgroundColor = UIColor.blue
            submitButton.addTarget(self, action: #selector(self.submitButtonPressed(_:)), for: .touchUpInside)

            customView.addSubview(commentText)
            customView.addSubview(submitButton)

            tableView.tableFooterView = customView

以下是截图中的结果:

我想做的是把页脚一直放在屏幕的底部,这可能吗?