title: How do I create a UI for a Many-to-Many relationship?
body: <p>Can anyone advise on the best way to create a UI for establishing Many-to-Many relationships ?</p>
  
  <p>Lets use an example from a previous question  List &lt;&lt;-->> Patient.</p>
  
  <p>I can create two separate Table Views, one for Lists and another for Patients which will allow the user to create Lists and Patients using two separately created Array Controllers (Lists and Patients), one linked to the List entity and other linked to the Patient entity.</p>
  
  <p>Now I would like to be able to add/remove Patients from a List by creating an Table View that shows only Patients in the selected List.  To do this I create a Array Controller (ListPatients) linked to the entity Patient with a Content Set binding to Lists.selection.patients.</p>
  
  <p>Now things stop working nicely from here on....</p>
  
  <p>If I bind a button to the ListPatients.add method then a NEW Patient gets created - there seems to be no way to simply add a NEW relationship between an existing Patient and the List.</p>
  
  <p>Ideally what I would like to be able to do is to have a drop down list to select the Patient from.</p>
  
  <p>Does anyone have any suggestions as to how best to do this without needing to create a new entity to represent this relationship.</p>