How to get previous selection from ion-selection

I’m writing a selection list to a firebase DB based on user selection:

<ion-select [(ngModel)]=“type”>

a
b
c
d

It’s saving to Firebase

This is the .ts calling the provider:

ionViewDidLeave() {
this.firebaseSvcProvider.addSettings(this.type)
.then( () => {
this.navCtrl.pop();
}, error => {
console.log(error);
});
}
this is from the provider.

    addSettings(type:string):
    firebase.Promise<any>{

return this.setSettings.push({ type }); }

But i’d like to retrieve the previously saved type to display on the page. And it’s created a new record every time. How do I get it to not create a new record but simply update the existing if there is a change and use the previous selection in the display?