How to display ionic2 Alert after Firebase changeEmail - firebase

Question

I have the following function to change the email on a Firebase user account. I want to display an ionic2 alert when complete, whether it was successful or there was an error. From my code below I do get the alert to display BUT it is blank. Most likely it is a timing issue on the Firebase promise but I don't know how to fix it.
private doChangeEmail(data): void {
var myAlert: {
title?: string,
subtitle?: string
} = {};
this.auth.ref.changeEmail({
oldEmail: data.oldemail,
newEmail: data.newemail,
password: data.password
}, function(error) {
if (error) {
switch (error.code) {
case "INVALID_PASSWORD":
myAlert.title = 'Invalid Password';
myAlert.subtitle = 'The specified user account password is incorrect.';
break;
case "INVALID_USER":
myAlert.title = 'Invalid User';
myAlert.subtitle = 'The specified user account does not exist.';
break;
default:
myAlert.title = 'Error creating user';
myAlert.subtitle = error;
}
} else {
myAlert.title = 'DONE';
myAlert.subtitle = 'User email changed successfully!';
}
});
let alert = Alert.create({
title: myAlert.title,
subTitle: myAlert.subtitle,
buttons: [{
text: 'OK',
handler: () => {
}
}]
});
this.nav.present(alert);
}

Answer 1

put the alert code inside the promise result....
this.auth.ref.changeEmail({
oldEmail: data.oldemail,
newEmail: data.newemail,
password: data.password
}, function(error) {
if (error){
// do error stuff..
} else {
// do success stuff..
}
// show alert here...
})

Answer 2

I found the following comment by Frank van Puffelen which solved my issue:
You're using this inside a callback function, where it has a different meaning. One solution is to use fat-arrow/rocket notation for the callback, which ensures this is what you expect it to be:
The correct syntax should be
this.auth.ref.changeEmail({
oldEmail: data.oldemail,
newEmail: data.newemail,
password: data.password
}, (error) => {
if (error){
// do error stuff..
} else {
// do success stuff..
}
// show alert here...
})
and the alert shows correclty as pointed out by Aaron Saunders