How to call toast in apex class?

Question

I have a Apex Trigger on creation of a record that calls an Apex class. The point of a method in the class is to check the current time of user and see if it is within business hours.

However, I want to display a toast (Either a warning or danger) if the user tries to input time outside of business hours. Is this possible?

Apex Code:

if (userTime > endTime && userTime < startTime)
    System.debug('YOU ARE OUT OF HOURS');
    //This is where I would like to call a toast

I have created toasts within lightning components and javascript controllers, but is it possible to do call the toast here? If so, how?

Answer 1

The short answer to this is "no, you cannot trigger a toast from Apex". This is because Apex is a server-side language and toasts must be launched from the front-end.

However, as @glls answer says, you can make a call to Apex, interpret its result, and then trigger a toast based on what results are. This is a very common pattern with errors, for example, where the Apex controller throws an exception and then that exception is shown to the user as a toast.

Here is a very brief example:

Apex:

public class myClass {
    @AuraEnabled
    public static String giveMeAMessage(String name) {
        return 'Hello ' + name;
    }
}

Lightning Aura Component:

callApex : function(component, event, helper) {
    var action = component.get('c.giveMeAMessage'); 

    action.setParams({
        "name" : 'MYNAME'
    });

    action.setCallback(this, function(a){
        var state = a.getState(); // get the response state
        if(state == 'SUCCESS') {
            helper.showToast(component, event, helper, a.getReturnValue());
        } else {
            helper.showToast(component, event, helper, 'ERROR');
        }
    });
    $A.enqueueAction(action);
}

showToast : function(component, event, helper, message) {
    var toastEvent = $A.get("e.force:showToast");
    toastEvent.setParams({
        "title": "Success!",
        "message": "The Controller said: " + message
    });
    toastEvent.fire();
}

PS: You probably don't want to put the code above straight into production... there are better ways to make the call to Apex, but I wanted to show a quick example. Trailhead has several trails that will help with that part, including this one, which was also linked to in @glls's answer to this post.

Answer 2

Normally, toasts are something that you do on the client, yes, you can trigger it with apex, you just need to have the apex class be invoked from the client and return a response that can be handled by your client side controller in order to trigger a toast you will have to use an @AuraEnabled decorator on your apex method and handle the response appropriately.

Connect to Salesforce with Server-Side Controllers should give you a head start on achievieving this functionality