So basically your “Inventory” is also a quest manager, sounds like a bad design concept to me. it makes no sense to make an “Inventory” an object soley designed to manage item also look through the players quests every time an item is added and see they have been complete. My way round means that the quest gets told when an item has been picked up and only that quest handles it.
Imagine if the player had say, 30 quests, and only 1 needed x items. Every single time an item was added / removed, you’d have to loop through all the quests to see if they need it.
Also now, every inventory class needs to know about quests, and therefore every time you create an inventory it needs to store quest information as well.
In any case, I’m sure you have a game working with your system and mine has been working fine up until now.
Here’s mine by the way:
Game overview 2016 03 04 - YouTube (Sorry for the bad sound)