Making a list a definite length with no repeated data

Question

I have a list tag that currently accepts repeats and as many objects as I will drop into it. Is there a simple way to make this where it will only accept four objects and no repeats?

Answer 1

Here is the code in my item renderer:
protected function hbox1_mouseDownHandler(event:MouseEvent):void{
                var target:Canvas = Canvas(event.currentTarget);
                var sourceObject:Lesson = new Lesson(data.lesson, data.lessonNumber);
                var dragSource:DragSource = new DragSource();
                dragSource.addData( sourceObject, "listCopy" );
                mx.managers.DragManager.doDrag(target, dragSource, event, null , -0, -0, 0.40, true );
Here are the two drag//drop handlers in my class:
                 * allows for 4 items on the list and no repeats
                private function dragDropHandler(event:DragEvent):void{
                    if (event.dragSource.hasFormat('listCopy'))
                        var newObj:Lesson;
                        newObj = event.dragSource.dataForFormat("listCopy") as Lesson;
                        model.selectedLessonList.addItem(newObj as Lesson);
                 * allows for 4 items on the list and no repeats
                   private function dragEnterHandler(event:DragEvent):void
                    tmpObject = event.dragSource.dataForFormat("listCopy");
                    if(tmpObject == null){return;}//something messed up!
                    trace(tmpObject.lesson);
                    repeatFlag = false;
                    for (var i:int=0; i < model.selectedLessonList.length;i++){
                        if (model.selectedLessonList[i].lesson == tmpObject.lesson){
                            repeatFlag=true;
                            break;
                    if (model.selectedLessonList.length < maxLength && repeatFlag==false){
                        DragManager.acceptDragDrop(List(event.target));       
                        DragManager.showFeedback(mx.managers.DragManager.COPY);
Here is the list containing the original item:
           <mx:List id="lstAllCategories" width="245" height="95%" itemRenderer="com.components.renderers.CategoryListItemRenderer"
                                dataProvider="{ApplicationModel.instance.categoryList}" styleName="BoxBackground"
                                rollOver="createToolTip('Mouse_Over_AllCategories')" rollOut="createToolTip('Mouse_Over_BottomOfScreen')">
Here is the list that the item is being dropped into:
<mx:List id="lstCurrentSelectedLessons" dataProvider="{model.selectedLessonList}" width="245" height="140"  dropEnabled="true" dragDrop="dragDropHandler(event);checkSelectedLessonList()" dragEnter="dragEnterHandler(event)"
                                doubleClickEnabled="true" doubleClick="beginLesson()" itemRenderer="com.components.renderers.ChosenListItemRenderer" styleName="BoxBackground"
                                rollOver="createToolTip('Mouse_Over_CurrentLessons')" rollOut="createToolTip('Mouse_Over_BottomOfScreen')">
                            </mx:List>