NPCs reacting to your presence

> north 
------------------------------------
Meadow
You are standing in a green meadow. 
A bandit is here. 
------------------------------------
Bandit gives you a menacing look!

This tutorial shows the implementation of an NPC object that responds to characters entering their location.

What we will need is the following:

• An NPC typeclass that can react when someone enters.

• A custom Room typeclass that can tell the NPC that someone entered.

• We will also tweak our default Character typeclass a little.

# in mygame/typeclasses/npcs.py  (for example)

from typeclasses.characters import Character

class NPC(Character):
    """
    A NPC typeclass which extends the character class.
    """
    def at_char_entered(self, character, **kwargs):
        """
        A simple is_aggressive check.
        Can be expanded upon later.
        """
        if self.db.is_aggressive:
            self.execute_cmd(f"say Graaah! Die, {character}!")
        else:
            self.execute_cmd(f"say Greetings, {character}!")

Passing extra information

Note that we don’t use the **kwargs property here. This can be used to pass extra information into hooks in your game and would be used when you make custom move commands. For example, if you run into the room, you could inform all hooks by doing obj.move_to(..., running=True). Maybe your librarian NPC should have a separate reaction for people running into their library!

We make sure to pass the **kwargs from the standard at_object_receive hook below.

Here we make a simple method on the NPC˙ called at_char_entered. We expect it to be called when a (player-)character enters the room. We don’t actually set the is_aggressive Attribute beforehand; we leave this up for the admin to activate in-game. if it’s not set, the NPC is simply non-hostile.

Whenever something enters the Room, its at_object_receive hook will be called. So we should override it.

# in mygame/typeclasses/rooms.py

from evennia import utils

# ... 

class Room(ObjectParent, DefaultRoom):

    # ... 
    
    def at_object_receive(self, arriving_obj, source_location, **kwargs):
        if arriving_obj.account: 
            # this has an active acccount - a player character
            for item in self.contents:
                # get all npcs in the room and inform them
                if utils.inherits_from(item, "typeclasses.npcs.NPC"):
                    item.at_char_entered(arriving_obj, **kwargs)

Universal Object methods

Remember that Rooms are Objects, and other Objects have these same hooks. So an at_object_receive hook will fire for you when you pick something up (making you ‘receive’ it). Or for a box when putting something inside it, for example.

A currently puppeted Character will have an .account attached to it. We use that to know that the thing arriving is a Character. We then use Evennia’s utils.inherits_from helper utility to get every NPC in the room can each of their newly created at_char_entered method.

Make sure to reload.

Let’s create an NPC and make it aggressive. For the sake of this example, let’s assume your name is “Anna” and that there is a room to the north of your current location.

> create/drop Orc:typeclasses.npcs.NPC
> north 
> south 
Orc says, Greetings, Anna!

Now let’s turn the orc aggressive.

> set orc/is_aggressive = True 
> north 
> south 
Orc says, Graah! Die, Anna!

That’s one easily aggravated Orc!