Adding current user to a TABLE Groups

Android
1

Hi, I’m trying to add users to a group using some kind of “unique value”, for example, my friend creates a group and I want to join it, he will need to send me a Code or URL so I can join it.

I started by creating a Table Groups on Backendless, I added a column “Users” to it, which uses my current Users, but I’m having problems at adding users on, I’ve tried a inviteID that corresponds to a uniqueValue, and I’ve tried the ObjectID, and I’m not having success with neither.

I’ll show some code below:

btnJoinGroup.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(etGroupId.getText().toString().isEmpty()){
Toast.makeText(FirstGroup.this, “Invite EMPTY!”, Toast.LENGTH_SHORT).show();
}
else{
String groupId = etGroupId.getText().toString().trim();
Backendless.Data.of(“Groups”).findById(groupId, new AsyncCallback<Map>() {
@Override
public void handleResponse(Map savedUser) {
Map user = (Map) Backendless.UserService.CurrentUser();
Backendless.Persistence.save(user, new AsyncCallback<Map>() {
@Override
public void handleResponse(Map response) {
Toast.makeText(FirstGroup.this, “Success!!”, Toast.LENGTH_SHORT).show();
}

@Override
public void handleFault(BackendlessFault fault) {
Toast.makeText(FirstGroup.this, “ERROR!”, Toast.LENGTH_SHORT).show();
}
});
}

@Override
public void handleFault(BackendlessFault fault) {
Toast.makeText(FirstGroup.this, “ERROU LOGO!”, Toast.LENGTH_SHORT).show();
}
});

}
}
});

}

Thank you for any help you guys are amazing :wink:
Alexandre Coutinho

2

Hi Alexandre,

Here’s the first problem that I see:

Backendless.Data.of(“Groups”).findById(groupId, new AsyncCallback<Map>() {
@Override
public void handleResponse(Map savedUser) {

Notice that you make a request to the Groups data table, and in the handleResponse you call the argument savedUser. This is wrong, since the response you get back would be a Map representing a group object.

Then in the same handleResponse callback, you do the following:

Map user = (Map) Backendless.UserService.CurrentUser();
Backendless.Persistence.save(user, new AsyncCallback<Map>() {

Well, that will do absolutely nothing useful. You take the currently logged in user and you just save it back into the database. What is that for?

Cheers,
Mark

3

I was trying to save the current user on the group that corresponds to the input code, I’m still having a lot of trouble here. The current user should be able to enter a given code (that corresponds to a group) and join that group.

Thanks Mark!
Alex

4

Okay, Alex. What would be the design at the data level? Do you understand how you could use table relations here?

5

Hi Mark,
No I don’t think I know how to use table relations…

6

Hi, Alexandre. If you want to associate current user with some group, existing in the corresponding table, you should use one of the next methods:

Backendless.Data.of( E ).addRelation( 
                                       E parentObject,
                                       String relationColumnName,
                                       Collection<T> children,
                                       AsyncCallback;Preformatted text<Integer> callback );

Backendless.Data.of( "TABLE-NAME" ).addRelation( 
                                                 Map parentObject,
                                                 String relationColumnName,
                                                 Collection<Map> children,
                                                 AsyncCallback<Integer> callback );

More information in SDK Documentation.

Feel free to ask more questions.

1 Like
7

Hey andrii thanks for the answer! I did a pause and yesterday got back to it, I think what you asked me to do is what I need to do, but I’m having trouble executing it, how can I get the objectId of a group on the groups table?

8

Hi, Alexandre. To find objectId you can use the next method:

Backendless.Data.of( Contact.class ).find( queryBuilder, 
                                           new AsyncCallback<List<Contact>>(){
  @Override
  public void handleResponse( List<Contact> foundContacts )
  {
  }
  @Override
  public void handleFault( BackendlessFault fault )
  {
  }
});

Find more in Documentation.

Regards, Andrii.

9

Hi Andrii, on that documentation I can’t find anything related to objectId, should I create a “whereClause” equals to “objectId”?

Thank you so much,
Alexandre

10

You can find the group by “name”, for example, or any other field.
Set whereClause: name = 'foo', use it for find() method and you’ll get an object, which will have ‘objectId’ field. Use this objectId for setting relations.

Regards, Andrii.

11

I just want to use the “group” object I’ve created in the database, I want to get this new created “group” and get it’s objectId, how can I save this objectId into a String? I’m having trouble accessing this new “group” after creating it so I’m unable to get an instance of its objectId.

I’ve tried some stuff like…
String groupObjectId = Backendless.Data.of("Groups").findLast().get("objectId").toString();
and…
String groupObjectId = (String) lastGroup.get("objectId");
and I’m always getting a null return.

12

Hi! Your code should work, please, give your AppId

13

FindLast() method right after saving a new ‘Group’ object is not a kind of approach you can rely on. First of all if this code goes right after async call for saving an object - findFirst() can be called before ‘Group’ object is actually saved in database.

As Mark recommended in one of your previous topics - use logic for getting objectId in handleResponse block of

Backendless.Data.of("Group").save(map, new AsyncCallback<Map>(){
      @Override
      public void handleResponse( Map response )
      {
          response.get("objectId");
      }
      @Override
      public void handleFault( BackendlessFault fault )
      {
      }
    });

Anton

14

With that code, how do I use the objectId as an instance String?

15

String objectId = response.get( "objectId" )