Dtyjlui

I am trying to display apex catch exception error message in lightning message.
I have tried below in helper. but it didn't work. And let me know how to call this from Lightning component.

Helper:

    saveAction.setCallback(this,function(response){

                    if (response.getState() == "SUCCESS") {

                    component.set("v.isShow",false);

                    var opportunitId = response.getReturnValue();

                    window.location.href = "/"+opportunitId;

                    }

                });

                $A.enqueueAction(saveAction);

Lightning Controller:

    saveRecord : function(component, event, helper)

        {

            helper.helperSave(component, event);

        }

two things,

In your apex handle the exception like so

try {

    // your code here

}

catch (Exception e //if you know what type of error it is going to throw you can be more specific ie. NullPointerException e) {

    // "Convert" the exception into an AuraHandledException

    throw new AuraHandledException(e.getMessage());    

}

Now you have to handle the error in the javascript controller

  saveAction.setCallback(this,function(response){

      let state = response.getState();          

      if (state == "SUCCESS") {

        component.set("v.isShow",false);

        var opportunitId = response.getReturnValue();

        var navEvt = $A.get("e.force:navigateToSObject");

        navEvt.setParams({

           "recordId": opportunityId

        });

        navEvt.fire();

       } else if(state = "ERROR"){

           errorMsg = response.getError()[0];

           let toastParams = {

             title: "Error",

             message: errorMsg, // Default error message

             type: "error"

            };

           let toastEvent = $A.get("e.force:showToast");

           toastEvent.setParams(toastParams);

           toastEvent.fire();

          }

        });

        $A.enqueueAction(saveAction);

    }

Also use the built in object redirect to navigate to the opportunity.

var navEvt = $A.get("e.force:navigateToSObject");

navEvt.setParams({

  "recordId": opportunityId

});

navEvt.fire();