Copy field from parent item on creation

Question

I know that I can reference a parent item with Glass Mapper, but I need to copy a specific field on my child because I need to facet on it.

What is the best way to copy a field from my parent item on creation?

Answer 1

You can add your own handler to item:created event and get the field value from parent.

First register your handler:

<event name="created">
  <handler type="YourNameSpace.YourHandler, YourAssembly" method="OnItemCreated" />
</event>

And the code:

namespace YourNamespace
{
    public class YourHandler
    {
        private static ID _childTemplateId = ID.Parse("YOUR_TEMPLATE_ID");
        private static ID _parentTemplateId = ID.Parse("YOUR_PARENT_TEMPLATE_ID");
        private const string FieldName = "YOUR_FIELD_NAME";

        public void OnItemCreated(object sender, EventArgs args)
        {
            try
            {
                using (new SecurityDisabler())
                {
                    ItemCreatedEventArgs arg = Event.ExtractParameter(args, 0) as ItemCreatedEventArgs;

                    if (arg == null || arg.Item == null || arg.Item.Parent == null)
                        return;

                    var item = arg.Item;
                    var parent = arg.Item.Parent;

                    if (item.TemplateID != _childTemplateId)
                        return;

                    if (parent.TemplateID != _parentTemplateId)
                        return;

                    if (item.Database.Name != "master")
                        return;

                    item.Editing.BeginEdit();
                    item[FieldName] = parent[FieldName];
                    item.Editing.EndEdit();
                }
            }
            catch (Exception exc)
            {
                Log.Error("Exception while copying field value from parent", exc);
            }
        }
    }
}