WKWebView禁止放大缩小(捏合手势)

在webView加载完毕之后，运行下面的JS代码禁止WKWebView放大缩小
//加载完毕

• (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation {
  NSString *injectionJSString = @"var script = document.createElement('meta');"
  "script.name = 'viewport';"
  "script.content="width=device-width, user-scalable=no";"
  "document.getElementsByTagName('head')[0].appendChild(script);";
  [webView evaluateJavaScript:injectionJSString completionHandler:nil];
  }