I am trying to use visualforce to show Note and Attachments as separate lists have the code below as the controller:

This works, however it returns the CreatedByID (00520000001U7ZIAA0) only and not the name.

  public List<Attachment> getAtt() {   
      return [SELECT ID, Name, Description, Body, CreatedByID, CreatedDate FROM Attachment WHERE ParentID = :FeedbackID  ORDER BY CreatedDate DESC ] ]
  }

I then tried to do a mp but i'm missing a step or logic somewhere to get the name of the user

  public List<Attachment> getAtt() {
      List <Attachment> a = [SELECT ID, Name, Description, Body, CreatedByID, CreatedDate FROM Attachment WHERE ParentID = :FeedbackID];
      SET<String> cList = new Set<String>();
          for (Attachment ac: a) {
          cList.add(ac.CreatedByID);
      }
      List <User> u = [SELECT ID, Name FROM User WHERE ID in :cList ];
      Map<String, String> CreatedByMap = new Map<String, String>();
      for (User cb :u) {
           CreatedByMap.put(cb.Id,cb.Name);//populate map
      }
      
      return [SELECT ID, Name, Description, Body, CreatedByID, CreatedDate FROM Attachment WHERE ParentID = :FeedbackID  ORDER BY CreatedDate DESC AND CreatedByID in :CreatedByMap ];
 
  }

 This gives an error: Error: Compile Error: IN operator must be used with an iterable expression at line 50 column 141 which is 

in :CreatedByMap ];

At the limit of my knowledge here so any help much appreciated.