Using string hashes for indexing quest state in TMap

Development Architectural and Design Visualization
1

Context

I’m trying to write my quest system and here’s the basic structure for a quest:

  • A quest is a C++ UObject that is composed, among other things, by objectives
  • Objectives are also UObjects. There is one base abstract class that represents an objective, and derived classes that represents objective types, such as reaching a location or killing an enemy.

I then created multiple blueprints extending my base quest, and due to the way I exposed the quest variables and objectives, I can use the editor to setup everything up for each quest and they are only instanced once the player accepts it. I have one blueprint for each quest in my game and so far it seems to work well.

My question

I’m now trying to save/load the quest state. My initial thoughts are to create a TMap in PlayerState and store the quest states in there (saving only the bare minimum, like what is the index for the current objective for a quest, how many enemies the player has killed already, or if the quest has been completed already).

While I could use the blueprints class for each quest as the key in TMap, that sounds like an overkill, so I was trying to find a way to automatically generate a ID for each quest in a consistent way, meaning that every blueprint quest class needs to map to a unique ID and it needs to be the same ID every time as I need to save this information and be able to retrieve it in a different play session.

My idea was to use the GetTypeHash function using the class name of each quest to generate an integer ID, but I don’t know how the hashing function for strings work in unreal or what are the changes for collisions.

Is that a good approach? Are there any other approaches I could consider?

2

Type hashing could work.

But you can also use Guid structure as a Key in the map and have a Guid ID = NewGuid() in your quest objectives to identify them.

3

GUID will vary between gameplays, I believe, and everytime the quest is instanced it will have a different ID. I was looking for a way to get the same ID everytime.

One of the reasons for that is that I intend to have quests that depend on other quests to be complete. If I can consistently map a quest to an Id, then when I’m creating a “child” class, I can provide the class of the quest it depends on, map that to an ID and query my state map if the desired quest has been complete already, for example

4

Guids will stay consistent if you store them in a UPROPERTY(EditDefaultsOnly) variable. When you create the Blueprint, you can assign a new guid to that property and it’ll stay that way just like any other property you set in a Blueprint asset.

Depending on your long-term plans, it might also be worth looking into primary asset ids. They work well with the Asset Manager, which is something you might have to consider 2 years from now when you have 200 quests you need to load without causing the framerate to suffer.

5

Asset ids look promising! I wasn’t aware they were a thing. I’m fairly new to unreal engine still trying to get used to all the available tools.

Thanks!