[SalesForce] How to assign a task to a queue

Rather than setting the Case.OwnerId to the Queue ID you need to set it to the Group ID. As OwnerId is a lookup to User and Group rather than User and Queue as displayed in the UI.

You can check it yourself using Workbench > Info > Standard & Custom Objects > Case, Fields > OwnerId > Reference To.

However by doing this you will receive a MIXED_DML_EXCEPTION due to executing DML on a setup object (inserting QueuesObject) between DML on non-setup objects (Group and Case) to get around this you need to execute the DML on setup objects in a different context, this can be done using System.runAs(...).

If you change it to the following it should work:

Group testGroup = new Group(Name='test group', Type='Queue');
insert testGroup;

System.runAs(new User(Id=UserInfo.getUserId()))
{
    QueuesObject testQueue = new QueueSObject(QueueID = testGroup.id, SObjectType = 'Case');
    insert testQueue;
}

Case aCase = new Case(OwnerId = testGroup.Id);
insert aCase;

I've done a bit of research on this myself.

There's another object called GroupMember which acts as a junction object between the User and the Group itself which contains the following fields:

• GroupId
• Id
• SystemModstamp
• UserOrGroupId

Running a query like the following:

SELECT GroupId,Id,SystemModstamp,UserOrGroupId FROM GroupMember WHERE GroupId = '00GD0000004HMw3MAG'

Will return a list of people in that particular group. The field UserOrGroupId holds the ID of the users within that particular group.

So what you would need to do is create a new GroupMember object, assigning the users to that particular group.

You'll first need to get the Id of the Group you want to assign people to and query that, then where you create. Something like this will work:

group = [SELECT Id FROM Group WHERE Name = 'Support Team 1'].Id;
user = [SELECT Id FROM User WHERE Name = 'John Smith' LIMIT 1].Id;

GroupMember gm = new GroupMember(
  GroupId = group;
  UserOrGroupId = user;
);

insert gm;