For loops not looping through each record in a list

Question

Background: I'm trying to write a handler class to create Chatter group members, I have a future method that works great for one group. However, my requirement is three groups and that's where it goes off the rails.

When it runs I get an the error:

Insert failed. First exception on row 3; first error: DUPLICATE_VALUE, User is already a Member of this group.: [MemberId]

Doing some debugs it wants to create 9 records, 3 sets of the 3 groups.

How can I loop through each object and add member records for each user/group combination?

 @future
public static void addToGroups(Set<Id> userIds)
{   
    // The users that will be added to the group
    List<User> users = [SELECT id, Username FROM User WHERE id in :userIds];

    // Find the Chatter group Ids from the names of the custom setting "Chatter Auto Follow"
    List<CollaborationGroup> chatterGroups = [SELECT Id, Name
                                              FROM CollaborationGroup 
                                              WHERE Name in :Chatter_Auto_Follow__c.getall().keySet()];

    // Get Chatter values
    List<Chatter_Auto_Follow__c> settings = [SELECT Name, Frequency__c FROM Chatter_Auto_Follow__c];

    // Create blank lists for inserting new records
    List<CollaborationGroupMember> chatterGroupMembers = new List<CollaborationGroupMember>();

    // loop the users that have been created
    for (User u : users)
    {
        // loop the custom setting records
        for(Chatter_Auto_Follow__c s : settings)
        {
            // loop the groups
            for (CollaborationGroup c : chatterGroups)
            {
                // add the user to the group
                CollaborationGroupMember cMember = new CollaborationGroupMember(
                    CollaborationGroupId = c.id,
                    MemberId = u.Id,
                    CollaborationRole = 'Standard',
                    NotificationFrequency = s.Frequency__c
                    );
                chatterGroupMembers.add(cMember);
            }
        }
    }
    System.debug('Members To Insert:: ' + chatterGroupMembers);
    insert chatterGroupMembers;
}

Answer 1

The users might already be members of a particular group; so just ignore the errors:

Database.insert(chatterGroupMembers, false);

If you're paranoid, you can check the return values from this method to make sure the error was DUPLICATE_VALUE and not any other type of error.

Answer 2

You need to check the list of existing collaboration member in each group before adding them newly. You could get an approach from this below code.

@future   
public static void addToGroups(Set<Id> userIds)
{
    // Find the Chatter group Ids from the names of the custom setting "Chatter Auto Follow"
    List<CollaborationGroup> chatterGroups = [SELECT Id 
                                              FROM CollaborationGroup 
                                              WHERE Name in :Chatter_Auto_Follow__c.getall().keySet()];
    Set<Id> settingsChatterGroupId = new Set<Id>();
    for(CollaborationGroup cgroup:chatterGroups)
    {
        settingsChatterGroupId.add(cgroup.Id);
    }

    // Query for existing chatter group records
    List<CollaborationGroupMember> cGMember = [SELECT   Id, 
                                                        MemberId,
                                                        CollaborationGroupId
                                               FROM     CollaborationGroupMember 
                                               WHERE    MemberId IN :userIds AND 
                                                        CollaborationGroupId IN :chatterGroups];

    System.debug('member size is:: ' + cGMember.size());

    //this will store existing members belong to each group.
    Map<Id, Set<Id>> mapCollabrUser = new Map<Id, Set<Id>>();

    if(cGMember.size()>0)
    {
        //loop through the group members
        for(CollaborationGroupMember gm:cGMember)
        {
            if(mapCollabrUser.containsKey(gm.CollaborationGroupId))
            {
                Set<Id> lst = mapCollabrUser.get(gm.CollaborationGroupId);
                lst.add(gm.MemberId);
                mapCollabrUser.put(gm.CollaborationGroupId,lst);                      
            }
            else
            {
                Set<Id> lst = new Set<Id>();
                lst.add(gm.MemberId);
                mapCollabrUser.put(gm.CollaborationGroupId,lst);    
            }
        }
    }

    List<CollaborationGroupMember> chatterGroupMembers = new List<CollaborationGroupMember>();

    for(Id userId:userIds)
    {
        //loop through the custom settings value
        for(Id cgroupSettingId: settingsChatterGroupId)
        {
            //check if this is existing CollaborationGroup
            if(mapCollabrUser.containsKey(cgroupSettingId))
            {
                //loop through the user list and find out user does not exist.
                for(CollaborationGroupId grpId:mapCollabrUser.keySet())
                {
                    //retrieve existing user list
                    Set<Id> setExistingUser = mapCollabrUser.get(grpId);

                    //if user does not belong to userlist of the group then add him.
                    if(!setExistingUser.contains(userId))
                    {
                        CollaborationGroupMember cMember = new CollaborationGroupMember(
                            CollaborationGroupId = grpId,
                            MemberId = userId,
                            CollaborationRole = 'Standard',
                            NotificationFrequency = s.Frequency__c
                            );
                        chatterGroupMembers.add(cMember);
                    }

                }
            }
            else
            {
                //this is of new entries which doesn't exist in database and add the new user
                CollaborationGroupMember cMember = new CollaborationGroupMember(
                    CollaborationGroupId = cgroupSettingId,
                    MemberId = userId,
                    CollaborationRole = 'Standard',
                    NotificationFrequency = s.Frequency__c
                    );
                chatterGroupMembers.add(cMember);
            }
        }
    }
    insert chatterGroupMembers;
}