trigger to add user to group based on profile

Question

I want to add users to a public group based on profile. This is what i have done so far.

trigger newUserTrigger on User (after insert) {
    string name = 'test Apex trigger';
    list<groupMember> groupList = new list<groupMember>();
    list<Group> grp = [select id from Group where name = : name];
    for(User us : trigger.new){
        if((us.profile.name == 'standard user') || (us.profile.name == 'standard platform user')){
            for(group g : grp){
                groupMember gp = new groupMember(groupId = g.Id);
                gp.UserOrGroupId = us.Id;
                groupList.add(gp);
            }
        }    
    }
    if(groupList.size() > 0)
    insert groupList;   
    }

I am not getting any error but the user is not getting added to the group.

Updated code

trigger newUserTrigger on User (after insert, after update) {

string name = 'test_Apex_trigger';
list<groupMember> groupList = new list<groupMember>();
list<Group> grp = [select id from Group where name = : name];
for(User us : trigger.new){
    System.debug('before if '+us.name);
     if(us.profile.name.equalsIgnoreCase('Standard User') || us.profile.name.equalsIgnoreCase('Standard Platform User')){
        system.debug('after if '+us.name);
        for(group g : grp){
            groupMember gp = new groupMember(groupId = g.Id);
            gp.UserOrGroupId = us.Id;
            groupList.add(gp);
        }
    }    
}
if(groupList.size() > 0)
insert groupList;   
}

There are no users in the user object

Answer 1

The most possible reason is that you never get into this loop:

for(group g : grp)

So no GroupMember records are created. You should make sure that a group with this name exists. Also, I'd recommend using DeveloperName field on group, since it is unique and Name is not.

Answer 2

Here is the updated code. Please try this.

trigger newUserTrigger on User (after insert, after update) {

string name = 'test_Apex_trigger';
list<groupMember> groupList = new list<groupMember>();
list<Group> grp = [select id from Group where name = : name];
Map<Id, Profile> profileIdMap = new Map<Id, Profile>([SELECT Id, name from profile]);
for(User us : trigger.new){
    System.debug('before if '+us.name);
     if(profileIdMap.get(us.profileid).name.equalsIgnoreCase('Standard User') || profileIdMap.get(us.profileid).name.equalsIgnoreCase('Standard Platform User')){
        system.debug('after if '+us.name);
        for(group g : grp){
            groupMember gp = new groupMember(groupId = g.Id);
            gp.UserOrGroupId = us.Id;
            groupList.add(gp);
        }
    }    
}
if(groupList.size() > 0)
insert groupList;   
}

Reason: In trigger.new, you cannot have the access to the reference field. You need to query it.