warning: parentheses were disambiguated as a function declaration
note: add a pair of parentheses to declare a variable
QNetworkRequest networkRequest(( QUrl(serverUrl) )); // QUrl加个括号就可以了 (意思应该就是如果不加括号,语法把你这个理解成了一种函数声明,所以下面才报没有对象)
networkRequest.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");