All in-game objects in Evennia, be it characters, chairs, monsters, rooms or hand grenades are represented by an Evennia Object. Objects form the core of Evennia and is probably what you’ll spend most time working with. Objects are Typeclassed entities.
An Evennia Object is, by definition, a Python class that includes
evennia.objects.objects.DefaultObject among its
parents. Evennia defines several subclasses of
evennia.objects.objects.DefaultCharacter - the normal in-game Character, controlled by a player.
evennia.objects.objects.DefaultRoom - a location in the game world.
evennia.objects.objects.DefaultExit - an entity that (usually) sits in a room and represents a one-way connection to another location.
You will usually not use the
Default* parents themselves. In
mygame/typeclasses/ there are
convenient subclasses to use. They are empty, and thus identical to
the defaults. Tweaking them is one of the main ways to customize you game!
How to create your own object types¶
You can easily add your own in-game behavior by either modifying one of the typeclasses in your game dir or by inheriting from them.
You can put your new typeclass directly in the relevant parent
module, or you could organize your code in some other way. Here we assume we make a new module
# mygame/typeclasses/flowers.py from typeclasses.objects import Object class Rose(Object): """ This creates a simple rose object """ def at_object_creation(self): "this is called only once, when object is first created" # add a persistent attribute 'desc' # to object (silly example). self.db.desc = "This is a pretty rose with thorns."
Now you just need to point to the class Rose with the
to make a new rose:
create command actually does is to use the evennia.create_object
function. You can do the same thing yourself in code:
from evennia import create_object new_rose = create_object("typeclasses.flowers.Rose", key="MyRose")
create command will auto-append the most likely path to your typeclass, if you enter the
call manually you have to give the full path to the class. The
create.create_object function is
powerful and should be used for all coded object creating (so this is what you use when defining
your own building commands).
This particular Rose class doesn’t really do much, all it does it make sure the attribute
desc(which is what the
look command looks for) is pre-set, which is pretty pointless since you
will usually want to change this at build time (using the
desc command or using the
Adding common functionality¶
Exit also inherit from
This is an empty ‘mixin’ class. Optionally, you can modify this class if you want to easily add some common functionality to all
your Objects, Characters, Rooms and Exits at once. You can still customize each subclass separately (see the Python
docs on multiple inheritance for details).
# in mygame/typeclasses/objects.py # ... from evennia.objects.objects import DefaultObject class ObjectParent: def at_pre_get(self, getter, **kwargs): # make all entities by default un-pickable return False class Object(ObjectParent, DefaultObject): # replaces at_pre_get with its own def at_pre_get(self, getter, **kwargs): return True # each in their respective modules ... class Character(ObjectParent, DefaultCharacter): # will inherit at_pre_get from ObjectParent pass class Exit(ObjectParent, DefaultExit): # Overrides and uses the DefaultExit version of at_pre_get instead def at_pre_get(self, getter, **kwargs): return DefaultExit.at_pre_get(self, getter, **kwargs)
Properties and functions on Objects¶
Beyond the properties assigned to all typeclassed objects (see that page for a list of those), the Object also has the following custom properties:
aliases- a handler that allows you to add and remove aliases from this object. Use
aliases.add()to add a new alias and
aliases.remove()to remove one.
location- a reference to the object currently containing this object.
homeis a backup location. The main motivation is to have a safe place to move the object to if its
locationis destroyed. All objects should usually have a home location for safety.
destination- this holds a reference to another object this object links to in some way. Its main use is for Exits, it’s otherwise usually unset.
nicks- as opposed to aliases, a Nick holds a convenient nickname replacement for a real name, word or sequence, only valid for this object. This mainly makes sense if the Object is used as a game character - it can then store briefer shorts, example so as to quickly reference game commands or other characters. Use nicks.add(alias, realname) to add a new one.
account- this holds a reference to a connected Account controlling this object (if any). Note that this is set also if the controlling account is not currently online - to test if an account is online, use the
accountfield is set and the account is online, this is a list of all active sessions (server connections) to contact them through (it may be more than one if multiple connections are allowed in settings).
has_account- a shorthand for checking if an online account is currently connected to this object.
contents- this returns a list referencing all objects ‘inside’ this object (i,e. which has this object set as their
exits- this returns all objects inside this object that are Exits, that is, has the
The last two properties are special:
cmdset- this is a handler that stores all command sets defined on the object (if any).
scripts- this is a handler that manages Scripts attached to the object (if any).
The Object also has a host of useful utility functions. See the function headers in
src/objects/objects.py for their arguments and more details.
msg()- this function is used to send messages from the server to an account connected to this object.
msgon all objects inside this object.
search()- this is a convenient shorthand to search for a specific object, at a given location or globally. It’s mainly useful when defining commands (in which case the object executing the command is named
callerand one can do
caller.search()to find objects in the room to operate on).
execute_cmd()- Lets the object execute the given string as if it was given on the command line.
move_to- perform a full move of this object to a new location. This is the main move method and will call all relevant hooks, do all checks etc.
clear_exits()- will delete all Exits to and from this object.
clear_contents()- this will not delete anything, but rather move all contents (except Exits) to their designated
delete()- deletes this object, first calling
The Object Typeclass defines many more hook methods beyond
at_object_creation. Evennia calls
these hooks at various points. When implementing your custom objects, you will inherit from the
base parent and overload these hooks with your own custom code. See
evennia.objects.objects for an
updated list of all the available hooks or the API for DefaultObject here.
There are three special subclasses of Object in default Evennia - Characters, Rooms and Exits. The reason they are separated is because these particular object types are fundamental, something you will always need and in some cases requires some extra attention in order to be recognized by the game engine (there is nothing stopping you from redefining them though). In practice they are all pretty similar to the base Object.
Characters are objects controlled by Accounts. When a new Account
logs in to Evennia for the first time, a new
Character object is created and
the Account object is assigned to the
account attribute. A
must have a Default Commandset set on itself at
creation, or the account will not be able to issue any commands! If you just
inherit your own class from
evennia.DefaultCharacter and make sure to use
super() to call the parent methods you should be fine. In
mygame/typeclasses/characters.py is an empty
Character class ready for you
Rooms are the root containers of all other objects. The only thing really separating a room from
any other object is that they have no
location of their own and that default commands like
creates objects of this class - so if you want to expand your rooms with more functionality, just
mygame/typeclasses/rooms.py is an empty
Room class ready for
you to modify.
Exits are objects connecting other objects (usually Rooms) together. An object named North or in might be an exit, as well as door, portal or jump out the window. An exit has two things that separate them from other objects. Firstly, their destination property is set and points to a valid object. This fact makes it easy and fast to locate exits in the database. Secondly, exits define a special Transit Command on themselves when they are created. This command is named the same as the exit object and will, when called, handle the practicalities of moving the character to the Exits’s destination - this allows you to just enter the name of the exit on its own to move around, just as you would expect.
The exit functionality is all defined on the Exit typeclass, so you could in principle completely
change how exits work in your game (it’s not recommended though, unless you really know what you are
doing). Exits are locked using an access_type called traverse and also make use of a few
hook methods for giving feedback if the traversal fails. See
evennia.DefaultExit for more info.
mygame/typeclasses/exits.py there is an empty
Exit class for you to modify.
The process of traversing an exit is as follows:
objsends a command that matches the Exit-command name on the Exit object. The cmdhandler detects this and triggers the command defined on the Exit. Traversal always involves the “source” (the current location) and the
destination(this is stored on the Exit object).
The Exit command checks the
traverselock on the Exit object
The Exit command triggers
at_traverse(obj, destination)on the Exit object.
object.move_to(destination)is triggered. This triggers the following hooks, in order:
obj.at_pre_move(destination)- if this returns False, move is aborted.
Move is performed by changing
obj.locationfrom source location to
On the Exit object,
at_post_traverse(obj, source)is triggered.
If the move fails for whatever reason, the Exit will look for an Attribute
err_traverse on itself
and display this as an error message. If this is not found, the Exit will instead call
at_failed_traverse(obj) on itself.