How do I reset Component Metadata field every time when component is re-opened?

Question

I have updated the logic to clear the field during display start event. Note: Updated my logic in readonly.js GUI extension

if($display)
{
   $evt.addEventHandler($display,start,ResetMetadataField)
}
Function ResetMetadataField()
{
  //code goes here
   var fieldBuilder = view.properties.fieldBuilder;
   var metadataTab = GetMetadataTab()
   if(metadataTab)
   {
     var fieldbuilder = GetMetadataFieldBuilder();
    //logic goes here to reset the metadata field
   }
}

But this code triggers during Save event as well. I need to reset the field only when component is re-opened but not on Save.

I am unable to differentiate between item re-open and other events like save,check-in..etc Is there a way to achieve the functionality?

Answer 1

Checkout the event system subscription. You probably need to subscribe to a specific event and not just run code according to a preset parameter.

This may well help as a starter: http://www.tridiondeveloper.com/intro-to-the-event-system