Zones

Say you create a room named Meadow in your nice big forest MUD. That’s all nice and dandy, but what if you, in the other end of that forest want another Meadow? As a game creator, this can cause all sorts of confusion. For example, teleporting to Meadow will now give you a warning that there are two Meadow s and you have to select which one. It’s no problem to do that, you just choose for example to go to 2-meadow, but unless you examine them you couldn’t be sure which of the two sat in the magical part of the forest and which didn’t.

Another issue is if you want to group rooms in geographic regions. Let’s say the “normal” part of the forest should have separate weather patterns from the magical part. Or maybe a magical disturbance echoes through all magical-forest rooms. It would then be convenient to be able to simply find all rooms that are “magical” so you could send messages to them.

Zones in Evennia

Zones try to separate rooms by global location. In our example we would separate the forest into two parts - the magical and the non-magical part. Each have a Meadow and rooms belonging to each part should be easy to retrieve.

Many MUD codebases hardcode zones as part of the engine and database. Evennia does no such distinction due to the fact that rooms themselves are meant to be customized to any level anyway. Below is a suggestion for how to implement zones in Evennia.

All objects in Evennia can hold any number of Tags. Tags are short labels that you attach to objects. They make it very easy to retrieve groups of objects. An object can have any number of different tags. So let’s attach the relevant tag to our forest:

forestobj.tags.add("magicalforest", category="zone")

You could add this manually, or automatically during creation somehow (you’d need to modify your @dig command for this, most likely). You can also use the default @tag command during building:

@tag forestobj = magicalforest : zone

Henceforth you can then easily retrieve only objects with a given tag:

import evennia
rooms = evennia.search_tag("magicalforest", category="zone")

Using typeclasses and inheritance for zoning

The tagging or aliasing systems above don’t instill any sort of functional difference between a magical forest room and a normal one - they are just arbitrary ways to mark objects for quick retrieval later. Any functional differences must be expressed using Typeclasses.

Of course, an alternative way to implement zones themselves is to have all rooms/objects in a zone inherit from a given typeclass parent - and then limit your searches to objects inheriting from that given parent. The effect would be similar but you’d need to expand the search functionality to properly search the inheritance tree.