It is important to note that your code will not work as expected because you are attempting to return a value from an observable which may not yet exist. One approach to handling this situation (though not the most optimal) is to store the observable in a service variable and provide a method to retrieve it. Below is a simplified example:
// Store data locally.
private data;
// Subscribe to the observable in the constructor and store the value locally.
constructor() {
this.item = this.af.database.object(path, {
preserveSnapshot: true
});
this.item.subscribe(snapshot => {
this.data = snapshot.val();
});
}
// Method to retrieve the data.
getData() { return this.data; }
However, using snapshots in this context is unnecessary. AngularFire provides observables that can be directly subscribed to like so:
constructor() {
this.item = this.af.database.object(path);
this.item.subscribe(data => this.data = data);
}
Alternatively, you can simplify it even further by doing:
constructor() {
this.af.database.object(path).subscribe(data => this.data = data);
}
One limitation of these approaches is that accessing the accessor will only give you the latest value, potentially causing issues if a new value arrives while the old one is still being used. To address this, simply return the observable from the service and consume it in the component.
// SERVICE
getData() { return this.af.database.object(path); }
// COMPONENT
public data;
ngOnInit() {
this.service.getData().subscribe(data => this.data = data);
}
<div>The data is {{data}}</div>
In conclusion, the recommended practice is to keep the observable as such until necessary and only unwrap it when needed, typically in the template using the async pipe for subscription management.
By following this pattern, you can effectively manipulate observable values without having to worry about memory leaks or managing subscriptions manually.