I've been rigorously testing the use of Required fields (Allow Nulls = No) in the Collector for ArcGIS application, and have discovered the following results for various field types:
-Short Integer fields: returns a space by default when a new feature is created
-Longs Integer fields: returns 0 by default when a new feature is created
-Double fields: returns 0.00 by default when a new feature is created
-Integer fields with an Range value domain: field returns the same default value if there was no domain when a new feature is created
-String fields with no domain: returns a default space when a new feature is created
-String fields with a coded value list domain: returns a blank or grayed out "No Value" text
After consulting with Esri, I was told that the coded list domains actually ARE returning a Null value when a new feature is created but no value has been selected. I am trying to determine the nature of this functionality, and whether it could be transferrable to the other field types either via development tools or in a future Esri software update. This situation has been maddening since it essentially means a field can only be effectively required if it is set to a coded value list domain (having a default value means the field no longer alerts the user it is required and allows them to skip the field, and would require the user to delete the default value in order to enter the correct value).
Any insight is appreciated!