Grabbing Keys with Firebase - firebase

Question

I'm currently creating an app using ionic2 and firebase for a class and I've run into an issue.
I"m not posting code because I don't have anything relevant enough to the question.
In my database I have a 'group' that people can create. I need the 'group' to be able to store a list of users. The way I'm currently doing it is that users will click an addGroup button, and the currentUser will be added to the list of users in that group simply by typing in the name of the group. (yeah i know that's going to need a password or something similar later, people obviously shouldn't just be able to join by group name)
*Names of groups will all be different so I should be able to query the database with that and get a single reference point.
The problem is that I don't know how to properly query the database and get the key value of the group object I want.
I keep looking things up and cant find a simple way to get the key of an object. I feel like this is a dumb question but, I'm unfamiliar with typescript, firebase, and ionic2 so I'm pretty lost in everything.

Answer 1

Answer for the question in comment.
you can query the database like this
this.group_val:any="group1"
let group=db.list('/groups', {
query: {
orderByChild: GroupName, //here specify the name of field in groups
equalTo: this.group_val //here specify the value u want to search
}
});
group.subscribe(grp=> {
//you can use the grup object here
})

Answer 2

First, define your database structure. The below is probably best:
groups
<first group> (Firebase-generated ID)
name: "Cat lovers"
users:
user1ID: true
user2ID: true
<second group>
...
I assume that when the user clicks on the group he wants to join, you know the group ID. For instance, it could be the value of an option in a select.
Get the list of groups:
groups$ = this.angularFireDatabase.list('groups');
To populate a list of groups into a select:
<select>
<option *ngFor="let group of groups$ | async" [value]="group.$key">
{{group.name}}
</option>
</select>
To create a new group:
groups$.push({name: "Dog lovers"})
The select (drop-down) will update itself.
To add a user to a group:
addUserToGroup(groupId, userId) {
this.angularFireDatabase.list(`groups/${groupID}/users`).update(userID, true);
}
To find a group based on its name:
// Define the shape of a group for better type checking.
interface Group { name: string; users: {[userId: string]: boolean;}; }
// Keep local list of groups.
groups$: FirebaseListObservable<Group>;
groups: Group[];
// Keep an updated local copy of groups.
ngOnInit() {
this.angularFireDatabase.list('groups').subscribe(groups => this.groups = groups);
}
function findGroupByName(name) {
return this.groups.find(group => group.name === name);
}