Here, I've written above expression is showing the error purpose. Let's assume you have pivot or straight objects on your dashboard. This scenario, your user want to put one error message like please select one dimension. Then might users can easily access what they're message showing
And class function we can use pick and match instead of if then we Are using the class function
For more information, you can take help from help.qlik.com
Best Anil, When applicable please mark the correct/appropriate replies as "solution" (you can mark up to 3 "solutions". Please LIKE threads if the provided solution is helpful