Get data from Firebase in Ionic 2 - firebase

Question

I have written my app with ionic 2 and followed the tutorial of Josh Morony, but I don't know how I can get a specific element from my firebase database.
For example I have this tree :
user
|__ (user_id)
|_ name : 'toto'
And so on...
I tried this way:
elt: FirebaseListObservable<any[]>;
this.elt = af.database.list('/user');
But how can I work with the selected data?

Answer 1

I found this solution which is similar than yours :
af.database.list('/user', { preserveSnapshot: true})
.subscribe(snapshots=>{
snapshots.forEach(snapshot => {
console.log(snapshot.key, snapshot.val());
this.items.push({
id: snapshot.key,
name: snapshot.val().name
});
});
});

Answer 2

In order to get the data as an array from a provider you need to return a promise which will be returned once the firebaseListObservable event is triggered with return data.
In your provider .ts
getData(fbPath): Promise<any> {
return new Promise(resolve => {
this.db.list(fbPath).subscribe(data => {
resolve(data);
})
})
}
Here the promise resolves once the data is populated and returns an array with easy access to the $value and $key properties. Which is ideal for creating conditionals or complex queries or a provider service with generic properties ( as opposed to querying the snapshot of the firebaseListObservable directly )
In your controller you can then write something like
this.providerName.getData('users').then(data => {
console.log('data',data);
})
This will return an object literal with the values
$exists
$key
$value
So now if you want a match conditional you can loop through the data with the match condition on the $key of the table users
if(myUserIdVar === data.$key){ // do something here };
A tidier syntax can be found using a library like lodash Where for example if you want a condition to match a stored id, say firebase.auth().currentUser.uid you can do a simple _.find
import { find } from 'lodash';
import * as firebase from 'firebase'; // Or just the firebase auth stuff
...
let filteredUser = find(data, ['$key', firebase.auth().currentUser.uid])
The $key value will be equal to the |__ (user_id) value

Answer 3

I think, af.database.list('/user') returns an Observable. You need to subscribe to it. Like this:
af.database.list('/user')
.subscribe(data => {
console.log("Data is : ",data);
},
(ex) => {
console.log('Found exception: ', ex);
});
Also, if this is in your provider and you want to return the data, you can create a new Observable and return it. If need help, could edit my answer to that also.