Conditionally changing ability to drag with dragHandle set does not work

[hbrysiewicz]

Since the drag handle functionality is configured in the didInsertElement hook (https://github.com/mharris717/ember-drag-drop/blob/master/addon/components/draggable-object.js#L27-L43) it is not possible to initially hide the handle, and then show it based on a selected state in the application.

For example, in my case, I have 3 columns, each a list. I only want the right column to be sortable when an item in the left column has been selected. When selecting from a left column, it drills down items in the adjacent right column.

Moving the logic in the didInsertElement hook instead to the didReceiveAttrs hook (with some added logic to ensure handlers aren't added when they already exist) fixes this problem as the binding would happen when state changed and the handle now appeared within the component.