语言：swift4.2
Xcode版本：10.1

demo地址：

https://github.com/colourfulStar/DynamicHeightSample

思路：

对webView的scrollView的contentSize添加监听。网页加载完成之后更新webView的frame

核心代码：

func createSubviews() {
        wkWebview.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 0)
        wkWebview.scrollView.showsHorizontalScrollIndicator = false
        wkWebview.scrollView.showsVerticalScrollIndicator = false
        wkWebview.scrollView.isScrollEnabled = false
        wkWebview.load(URLRequest.init(url: URL.init(string: "https://www.jianshu.com/p/492fafa6df48")!))
        wkWebview.scrollView.addObserver(self, forKeyPath: "contentSize", options: NSKeyValueObservingOptions.new, context: nil)
    }

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        let point = change![NSKeyValueChangeKey.init(rawValue: "new")]
        if point is CGSize {
            let height = (point as! CGSize).height
            var frame = self.wkWebview.frame
            frame.size.height = height
            self.wkWebview.frame = frame
            self.mainTableView.tableFooterView = self.wkWebview
        }
    }