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Finish up doc on sittables

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docs/source/Howto/Starting/Part3/A-Sittable-Object.md
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@ -1,3 +1,5 @@
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# Making a sittable object
In this lesson we will go through how to make a chair you can sit on. Sounds easy, right?
@ -13,9 +15,19 @@ The goals of this lesson are as follows:
- When you sit down you should not be able to walk to another room without first standing up.
- A character should be able to stand up and move away from the chair.
There are two main ways to design the commands for sitting and standing up.
- You can store the commands on the chair so they are only available when a chair is in the room
- You can store the commands on the Character so they are always available and you must always specify
which chair to sit on.
Both of these are very useful to know about, so in this lesson we'll try both. But first
we need to handle some basics.
## Don't move us when resting
This requires a change to our Character typeclass. Open `mygame/characters.py`:
When you are sitting in a chair you can't just walk off without first standing up.
This requires a change to our Character typeclass. Open `mygame/typeclasses/characters.py`:
```python
@ -42,9 +54,9 @@ to determine if we are stuck on the chair or not.
## Making the Chair itself
First we need the Chair itself. Since we want this to do some extra coded actions when
you sit in it, we can't just use a default Object. We need a new, custom Typeclass.
Create a new module `mygame/typeclasses/sittables.py` with the following content:
Next we need the Chair itself, or rather a whole family of "things you can sit on" that we will call
_sittables_. We can't just use a default Object since we want a sittable to contain some custom code. We need
a new, custom Typeclass. Create a new module `mygame/typeclasses/sittables.py` with the following content:
```python
@ -99,7 +111,7 @@ One could imagine that one could have the future `sit` command check if someone
chair instead. This would work too, but letting the `Sittable` class handle the logic around who can sit on it makes
logical sense.
We let the typeclass handle the logic, we also let it do all the return messaging. This makes it easy to churn out
We let the typeclass handle the logic, and also let it do all the return messaging. This makes it easy to churn out
a bunch of chairs for people to sit on. But it's not perfect. The `Sittable` class is general. What if you want to
make an armchair. You sit "in" an armchair rather than "on" it. We _could_ make a child class of `Sittable` named
`SittableIn` that makes this change, but that feels excessive. Instead we will make it so that Sittables can
@ -157,7 +169,7 @@ class Sittable(DefaultObject):
```
We added a new Attribute `adjective` which will probably usually be `in` or `on` but could also be `at` if you
want to be able to sit at a `desk` for example. A regular builder would use it like this:
want to be able to sit _at a desk_ for example. A regular builder would use it like this:
> create/drop armchair : sittables.Sittable
> set armchair/adjective = in
@ -167,7 +179,7 @@ sit down?
You sit down and a whoopie cushion makes a loud fart noise!
For this we needs to allow some further customization. Let's let the current strings be defaults that
For this we need to allow some further customization. Let's let the current strings be defaults that
we can replace.
```python
@ -256,19 +268,18 @@ class Sittable(DefaultObject):
stander.msg(f"You stand up from {self.key}")
```
Here we really went all out with flexibility. We added a bunch of optional Attributes to
hold alternative versions of all the messages. There are some things to note:
Here we really went all out with flexibility. If you need this much is up to you.
We added a bunch of optional Attributes to hold alternative versions of all the messages.
There are some things to note:
- We don't actually initiate those Attributes in `at_object_creation`. This is a simple
optimization. The assumption is that _most_ chairs will probably not be this customized.
So initiating to, say, empty strings would be a lot of useless database calls. The drawback
is that the available Attributes become less visible when reading the code. So we add a long
So initiating a bunch of Attributes to, say, empty strings would be a lot of useless database calls.
The drawback is that the available Attributes become less visible when reading the code. So we add a long
describing docstring to the end to explain all you can use.
- We use `.format` to inject formatting-tokens in the text. The good thing about such formatting
markers is that they are _optional_. They are there if you want them, but Python will not complain
if you don't include some or any of them.
Let's actually create the chair now so we can test it later.
if you don't include some or any of them. Let's see an example:
> reload # if you have new code
> create/drop armchair : sittables.Sittable
@ -276,9 +287,9 @@ Let's actually create the chair now so we can test it later.
> set armchair/msg_sitting_down = As you sit down {adjective} {key}, life feels easier.
> set armchair/msg_standing_up = You stand up from {key}. Life resumes.
We could have skipped `{key}` and `{adjective}` if we wanted. Whenever the message is returned, the format-tokens
within weill be replaced with `armchair` and `in` respectively. Should we rename the chair later, this will
show in the messages automatically (since `{key}` will change).
The `{key}` and `{adjective}` are examples of optional formatting markers. Whenever the message is
returned, the format-tokens within will be replaced with `armchair` and `in` respectively. Should we
rename the chair later, this will show in the messages automatically (since `{key}` will change).
We have no Command to use this chair yet. But we can try it out with `py`:
@ -293,26 +304,18 @@ We have no Command to use this chair yet. But we can try it out with `py`:
If you follow along and get a result like this, all seems to be working well!
## Deciding on a sitting command
## Command variant 1: Commands on the chair
We already know what our `sit` command must do:
This way to implement `sit` and `stand` puts new cmdsets on the Sittable itself.
As we've learned before, commands on objects are made available to others in the room.
This makes the command easy but instead adds some complexity in the management of the CmdSet.
- It needs to somehow figure out what object to sit on
- Once it finds a suitable sittable, it should call `sittable.do_sit(caller)`. The
object does the rest from there.
There are a few ways to do a Command like this. We'll explore the two main ones.
### Command variant 1: Command on the Chair
We can put the `sit` command in a command-set _on_ the chair. As we've learned before, commands on
objects are made available to others in the room. This makes the command easy. In combination with our
new `armchair`:
This is how it will look if `armchair` is in the room:
> sit
As you sit down in armchair, life feels easier.
What happens if there are also a sittable `sofa` and `barstool` in the room? Evennia will automatically
What happens if there are sittables `sofa` and `barstool` also in the room? Evennia will automatically
handle this for us and allow us to specify which one we want:
> sit
@ -323,14 +326,14 @@ handle this for us and allow us to specify which one we want:
> sit-1
As you sit down in armchair, life feels easier.
This is how we'd implement this type of command. To keep things separate we'll make a new module
`mygame/commands/sittables.py`
To keep things separate we'll make a new module `mygame/commands/sittables.py`:
```sidebar:: Separate Commands and Typeclasses?
You can organize these things as you like. If you wanted you could also put the sit-command + cmdset
You can organize these things as you like. If you wanted you could put the sit-command + cmdset
together with the `Sittable` typeclass in `mygame/typeclasses/sittables.py`. That has the advantage of
keeping everything related to sitting in one place.
keeping everything related to sitting in one place. But there is also some organizational merit to
keeping all Commands in one place as we do here.
```
@ -399,16 +402,26 @@ We could also update all existing sittables (all on one line):
> py from typeclasses.sittables import Sittable ;
[sittable.at_object_creation() for sittable in Sittable.objects.all()]
> The above shows an example of a _list comprehension_. Think of it as an efficient way to construct a new list
all in one line. You can read more about list comprehensions
[here in the Python docs](https://docs.python.org/3/tutorial/datastructures.html#list-comprehensions).
We should now be able to use `sit` while in the room with the armchair.
> sit
As you sit down in armchair, life feels easier.
> stand
You stand up from armchair.
One issue with placing the `sit` (or `stand`) Command "on" the chair is that it will not be available when in a
room without a Sittable object:
> sit
Command 'sit' is not available. ...
This is practical but not so good-looking; it makes it harder for the user to know a `sit` action is at all possible.
Here is a trick for fixing this. Let's add another Command to the bottom of `mygame/commands/sittables.py`:
This is practical but not so good-looking; it makes it harder for the user to know a `sit` action is at all
possible. Here is a trick for fixing this. Let's add _another_ Command to the bottom
of `mygame/commands/sittables.py`:
```python
# ...
@ -433,11 +446,11 @@ added `stand` to its `aliases`. In the command we look at `self.cmdname`, which
_actually used_ to call this command. We use this to return different messages.
We don't need a separate CmdSet for this, instead we will add this
to the default Character cmdset. Open `mygame/commands/default_cmdsets`:
to the default Character cmdset. Open `mygame/commands/default_cmdsets.py`:
```python
# ...
from commands.sittables import CmdNoSitStand
from commands import sittables
class CharacterCmdSet(CmdSet):
"""
@ -445,7 +458,7 @@ class CharacterCmdSet(CmdSet):
"""
def at_cmdset_creation(self):
# ...
self.add(CmdNoSitStand)
self.add(sittables.CmdNoSitStand)
```
@ -465,9 +478,9 @@ default error message is shown.
How does this work? There are two cmdsets at play, both of which have a `sit` Command. As you may remember we
set the chair's cmdset to `priority = 1`. This is where that matters. The default Character cmdset has a
priority of 0. This means that whenever we enter a room with a Sittable thing, _its_ cmdset will take
_precedence_ over the Character cmdset. So we are actually picking different `sit` commands
depending on circumstance. The user will never be the wiser.
priority of 0. This means that whenever we enter a room with a Sittable thing, the `sit` command
from _its_ cmdset will take _precedence_ over the Character cmdset's version. So we are actually picking
_different_ `sit` commands depending on circumstance! The user will never be the wiser.
So this handles `sit`. What about `stand`? That will work just fine:
@ -511,9 +524,9 @@ class CmdStand(Command):
# ...
```
We define a [Lock](../../../Components/Locks) on the command. The `cmd:` is in what situation Evennia will check the lock. The `cmd`
means that it will check the lock when determining if a user has access to this command or not. What will be
checked is the `sitsonthis` _lock function_ which doesn't exist yet.
We define a [Lock](../../../Components/Locks) on the command. The `cmd:` is in what situation Evennia will check
the lock. The `cmd` means that it will check the lock when determining if a user has access to this command or not.
What will be checked is the `sitsonthis` _lock function_ which doesn't exist yet.
Open `mygame/server/conf/lockfuncs.py` to add it!
@ -521,15 +534,28 @@ Open `mygame/server/conf/lockfuncs.py` to add it!
"""
(module lockstring)
"""
# ...
def sitsonthis(accessing_obj, accessed_obj, *args, **kwargs):
"""
True if accessing_obj is sitting on/in the accessed_obj.
"""
return accessed_obj.db.sitting == accessing_obj
# ...
```
Evennia knows that all functions in `mygame/server/conf/lockfuncs` should be possible to use in a lock definition.
The arguments are required and Evennia will pass all relevant objects to them:
```sidebar:: Lockfuncs
Evennia provides a large number of default lockfuncs, such as checking permission-levels,
if you are carrying or are inside the accessed object etc. There is no concept of 'sitting'
in default Evennia however, so this we need to specify ourselves.
```
- `accessing_obj` is the one trying to access the lock. So us, in this case.
- `accessed_obj` is the entity we are trying to gain a particular type of access to. So the chair.
- `args` is a tuple holding any arguments passed to the lockfunc. Since we use `sitsondthis()` this will
@ -551,20 +577,20 @@ caveats though that one needs to keep in mind.
We'll now try another way to add the `sit/stand` commands.
### Command variant 2: Command on Character
## Command variant 2: Command on Character
Before we start with this, delete the chairs you've created (`del armchair` etc) and then do the following
changes:
- In `mygame/typeclasses/sittables.py`, comment out the line `self.cmdset.add_default(CmdSetSit)`.
- In `mygame/commands/default_cmdsets.py`, comment out the line `self.add(CmdNoSitStand)`.
- In `mygame/commands/default_cmdsets.py`, comment out the line `self.add(sittables.CmdNoSitStand)`.
This disables the on-object command solution so we can try an alternative. Make sure to `reload` so the
changes are known to Evennia.
In this variation we will put the `sit` and `stand` commands on the `Character` instead of on the chair. This
makes some things easier, but makes the Commands themselves more complex because they will not know which
chair to sit on. We can't just do `sit` anymore. We need this:
chair to sit on. We can't just do `sit` anymore. This is how it will work.
> sit <chair>
You sit on chair.
@ -713,7 +739,7 @@ class CmdStand2(Command):
# find the thing we are sitting on/in, by finding the object
# in the current location that as an Attribute "sitter" set
# to the caller
sittable = self.caller.search(
sittable = caller.search(
caller,
candidates=caller.location.contents,
attribute_name="sitter",
@ -726,4 +752,51 @@ class CmdStand2(Command):
```
This forced us to to use the full power of the ``
This forced us to to use the full power of the `caller.search` method. If we wanted to search for something
more complex we would likely need to break out a [Django query](../Part1/Django-queries) to do it. The key here is that
we know that the object we are looking for is a `Sittable` and that it must have an Attribute named `sitter`
which should be set to us, the one sitting on/in the thing. Once we have that we just call `.do_stand` on it
and let the Typeclass handle the rest.
All that is left now is to make this available to us. This type of Command should be available to us all the time
so we can put it in the default Cmdset` on the Character. Open `mygame/default_cmdsets.py`
```python
# ...
from commands import sittables
class CharacterCmdSet(CmdSet):
"""
(docstring)
"""
def at_cmdset_creation(self):
# ...
self.add(sittables.CmdSit2)
self.add(sittables.CmdStand2)
```
Now let's try it out:
> reload
> create/drop sofa : sittables.Sittable
> sit sofa
You sit down on sofa.
> stand
You stand up from sofa.
## Conclusions
In this lesson we accomplished quite a bit:
- We modified our `Character` class to avoid moving when sitting down.
- We made a new `Sittable` typeclass
- We tried two ways to allow a user to interact with sittables using `sit` and `stand` commands.
Eagle-eyed readers will notice that the `stand` command sitting "on" the chair (variant 1) would work just fine
together with the `sit` command sitting "on" the Character (variant 2). There is nothing stopping you from
mixing them, or even try a third solution that better fits what you have in mind.
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