Error while executing showtoast in salesforce lightning - salesforce

Question

Below code throws an error while executing toastEvent.setParams statement. Not sure what I have missed or is it deprecated in spring'19 ?
loadContacts : function(cmp) {
var action = cmp.get("c.getContacts");
action.setCallback(this, function(response){
var state = response.getState();
if (state === 'SUCCESS') {
cmp.set('v.contacts', response.getReturnValue());
cmp.set('v.contactList', response.getReturnValue());
this.updateTotal(cmp);
}
console.log('Here');
var toastEvent = $A.get("e.force:showToast");
if (state === 'SUCCESS') {
toastEvent.setParams({
"title" : 'Success!',
"message" : 'Your contacts have been loaded successfully.'
});
}
else {
toastEvent.setParams({
"title" : "Error!",
"message" : "Something has gone wrong."
});
}
toastEvent.fire();
});
$A.enqueueAction(action);
},
Here is the screenshot of the error:

Answer 1

You can use lightning:notificationsLibrary. In your aura component, add:
<lightning:notificationsLibrary aura:id="notifLib"/>
And change your helper method to:
loadContacts : function(cmp) {
var action = cmp.get("c.getContacts");
action.setCallback(this, function(response){
var state = response.getState();
if (state === 'SUCCESS') {
cmp.set('v.contacts', response.getReturnValue());
cmp.set('v.contactList', response.getReturnValue());
this.updateTotal(cmp);
}
console.log('Here');
var toastEvent = $A.get("e.force:showToast");
if (state === 'SUCCESS') {
cmp.find('notifLib').showToast({
"title" : 'Success!',
"message" : 'Your contacts have been loaded successfully.'
"variant": 'success',
"mode": 'sticky'
});
}
else {
cmp.find('notifLib').showToast({
"title" : "Error!",
"message" : "Something has gone wrong."
"variant": 'error',
"mode": 'sticky'
});
}
});
$A.enqueueAction(action);
},

Answer 2

From the docs:
This event is handled by the one.app container. It’s supported in Lightning Experience, Salesforce app, and Lightning communities.
That error will pop up when you attempt to grab $A.get("e.force:showToast") outside of the one.app container context (e.g., if you have your component in a Lightning App for testing instead of dragging it on to a record page in the builder). $A.get("e.force:showToast") comes back as undefined, and calling setParams on undefined throws the error.
Try dragging your component onto a record detail page or a community, or create a tab from the Lighting component. If you need to use the component outside of the one.app context, you'll need to implement the show/hide toast logic yourself.