Fun with Delphi RTTI – Building a TreeView with all your classes

October 4, 2010 by Rodrigo 3 Comments

Do you remember the great posters  that came with older versions of delphi?

Now you can build your own tree of classes using the new rtti, here I leave the source code

uses
Rtti;

procedure FillTreeClasses(TreeViewClasses:TTreeView);

        //function to get the node wich match with the TRttiType
        function FindTRttiType(lType:TRttiType):TTreeNode;
        var
          i        : integer;
          Node     : TTreeNode;
        begin
           Result:=nil;
             for i:=0 to TreeViewClasses.Items.Count-1 do
             begin
                Node:=TreeViewClasses.Items.Item[i];
                if Assigned(Node.Data) then
                 if lType=TRttiType(Node.Data) then
                 begin
                  Result:=Node;
                  exit;
                 end;
             end;
        end;

        //function to get the node wich not match with the BaseType of the Parent
        function FindFirstTRttiTypeOrphan:TTreeNode;
        var
          i        : integer;
          Node     : TTreeNode;
          lType    : TRttiType;
        begin
           Result:=nil;
             for i:=0 to TreeViewClasses.Items.Count-1 do
             begin
                 Node :=TreeViewClasses.Items[i];
                 lType:=TRttiType(Node.Data);

                if not Assigned(lType.BaseType) then Continue;

                if lType.BaseType<>TRttiType(Node.Parent.Data) then
                begin
                   Result:=Node;
                   break;
                 end;
             end;
        end;

var
  ctx      : TRttiContext;
  TypeList : TArray<TRttiType>;
  lType    : TRttiType;
  PNode    : TTreeNode;
  Node     : TTreeNode;
begin
  ctx := TRttiContext.Create;
  TreeViewClasses.Items.BeginUpdate;
  try
    TreeViewClasses.Items.Clear;

      //Add Root, TObject
      lType:=ctx.GetType(TObject);
      Node:=TreeViewClasses.Items.AddObject(nil,lType.Name,lType);

      //Fill the tree with all the classes
      TypeList:= ctx.GetTypes;
      for lType in TypeList do
        if lType.IsInstance then
        begin
             if Assigned(lType.BaseType) then
             TreeViewClasses.Items.AddChildObject(Node,lType.Name,lType);
        end;

      //Sort the classes
      Repeat
         Node:=FindFirstTRttiTypeOrphan;
         if Node=nil then break;
         //get the location of the node containing the BaseType
         PNode:=FindTRttiType(TRttiType(Node.Data).BaseType);
         //Move the node to the new location
         Node.MoveTo(PNode,naAddChild);
      Until 1<>1;

  finally
    TreeViewClasses.Items.EndUpdate;
    ctx.Free;
  end;
end;

When you run this code the output will look like this