swift 笔记：iOS与JavaScript的交互（二）：JavaScriptCore：17。 JSExport相关演示

Posted 2021-05-19

// JSExport 协议定义
@objc protocol JSMethodsProtocol: JSExport {
  func alert(message: String)
}

// 当前 ViewController 继承 JSExport 协议：JSMethodsProtocol
class UIWebVIewWithJSExport: UIViewController, JSMethodsProtocol {
    //...
    func alert(message: String) {
    DispatchQueue.main.async(execute: {
      let ac = UIAlertController(title: "invokedByJavaScript", message: message, preferredStyle: .alert)
      let action = UIAlertAction(title: "ok", style: .default)
      ac.addAction(action)
      self.present(ac, animated: true)
    })
  }
}

// 在 webViewDidFinishLoad 的 Delegate 中暴露
extension UIWebVIewWithJSExport: UIWebViewDelegate {
  func webViewDidFinishLoad(_ webView: UIWebView) {
    self.navigationItem.title = webView.stringByEvaluatingJavaScript(from: "document.title")
    
    context = webView.value( 
      forKeyPath: "documentView.webView.mainFrame.javaScriptContext"
     ) as? JSContext
    
    //...
    // 将当前 ViewController 以 JSBridge 暴露出去
    context?.setObject(
      self, forKeyedSubscript: "jsBridge" as NSCopying & NSObjectProtocol
    )
  }
}