<h1>Objects<aclass="headerlink"href="#objects"title="Permalink to this headline">¶</a></h1>
<p>All in-game objects in Evennia, be it characters, chairs, monsters, rooms or hand grenades are represented by an Evennia <em>Object</em>. Objects form the core of Evennia and is probably what you’ll spend most time working with. Objects are <aclass="reference internal"href="Typeclasses.html"><spanclass="doc">Typeclassed</span></a> entities.</p>
<h2>How to create your own object types<aclass="headerlink"href="#how-to-create-your-own-object-types"title="Permalink to this headline">¶</a></h2>
<p>An Evennia Object is, per definition, a Python class that includes <codeclass="docutils literal notranslate"><spanclass="pre">evennia.DefaultObject</span></code> among its parents. In <codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/objects.py</span></code> there is already a class <codeclass="docutils literal notranslate"><spanclass="pre">Object</span></code> that inherits from <codeclass="docutils literal notranslate"><spanclass="pre">DefaultObject</span></code> and that you can inherit from. You can put your new typeclass directly in that module or you could organize your code in some other way. Here we assume we make a new module <codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/flowers.py</span></code>:</p>
<spanclass="s2">"this is called only once, when object is first created"</span>
<spanclass="c1"># add a persistent attribute 'desc'</span>
<spanclass="c1"># to object (silly example).</span>
<spanclass="bp">self</span><spanclass="o">.</span><spanclass="n">db</span><spanclass="o">.</span><spanclass="n">desc</span><spanclass="o">=</span><spanclass="s2">"This is a pretty rose with thorns."</span>
</pre></div>
</td></tr></table></div>
<p>You could save this in the <codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/objects.py</span></code> (then you’d not need to import <codeclass="docutils literal notranslate"><spanclass="pre">Object</span></code>) or you can put it in a new module. Let’s say we do the latter, making a module <codeclass="docutils literal notranslate"><spanclass="pre">typeclasses/flowers.py</span></code>. Now you just need to point to the class <em>Rose</em> with the <codeclass="docutils literal notranslate"><spanclass="pre">@create</span></code> command to make a new rose:</p>
<p>What the <codeclass="docutils literal notranslate"><spanclass="pre">@create</span></code> command actually <em>does</em> is to use <codeclass="docutils literal notranslate"><spanclass="pre">evennia.create_object</span></code>. You can do the same thing yourself in code:</p>
<p>(The <codeclass="docutils literal notranslate"><spanclass="pre">@create</span></code> 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 <codeclass="docutils literal notranslate"><spanclass="pre">create.create_object</span></code> function is powerful and should be used for all coded object creating (so this is what you use when defining your own building commands). Check out the <codeclass="docutils literal notranslate"><spanclass="pre">ev.create_*</span></code> functions for how to build other entities like <aclass="reference internal"href="Scripts.html"><spanclass="doc">Scripts</span></a>).</p>
<p>This particular Rose class doesn’t really do much, all it does it make sure the attribute <codeclass="docutils literal notranslate"><spanclass="pre">desc</span></code>(which is what the <codeclass="docutils literal notranslate"><spanclass="pre">look</span></code> command looks for) is pre-set, which is pretty pointless since you will usually want to change this at build time (using the <codeclass="docutils literal notranslate"><spanclass="pre">@desc</span></code> command or using the <aclass="reference internal"href="Spawner-and-Prototypes.html"><spanclass="doc">Spawner</span></a>). The <codeclass="docutils literal notranslate"><spanclass="pre">Object</span></code> typeclass offers many more hooks that is available to use though - see next section.</p>
<h2>Properties and functions on Objects<aclass="headerlink"href="#properties-and-functions-on-objects"title="Permalink to this headline">¶</a></h2>
<p>Beyond the properties assigned to all <aclass="reference internal"href="Typeclasses.html"><spanclass="doc">typeclassed</span></a> objects (see that page for a list of those), the Object also has the following custom properties:</p>
<ulclass="simple">
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">aliases</span></code> - a handler that allows you to add and remove aliases from this object. Use <codeclass="docutils literal notranslate"><spanclass="pre">aliases.add()</span></code> to add a new alias and <codeclass="docutils literal notranslate"><spanclass="pre">aliases.remove()</span></code> to remove one.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">location</span></code> - a reference to the object currently containing this object.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">home</span></code> is a backup location. The main motivation is to have a safe place to move the object to if its <codeclass="docutils literal notranslate"><spanclass="pre">location</span></code> is destroyed. All objects should usually have a home location for safety.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">destination</span></code> - this holds a reference to another object this object links to in some way. Its main use is for <aclass="reference external"href="/Objects.html#Exits">Exits</a>, it’s otherwise usually unset.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">nicks</span></code> - as opposed to aliases, a <aclass="reference internal"href="Nicks.html"><spanclass="doc">Nick</span></a> 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.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">account</span></code> - this holds a reference to a connected <aclass="reference internal"href="Accounts.html"><spanclass="doc">Account</span></a> controlling this object (if any). Note that this is set also if the controlling account is <em>not</em> currently online - to test if an account is online, use the <codeclass="docutils literal notranslate"><spanclass="pre">has_account</span></code> property instead.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">sessions</span></code> - if <codeclass="docutils literal notranslate"><spanclass="pre">account</span></code> field is set <em>and the account is online</em>, 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).</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">has_account</span></code> - a shorthand for checking if an <em>online</em> account is currently connected to this object.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">contents</span></code> - this returns a list referencing all objects ‘inside’ this object (i,e. which has this object set as their <codeclass="docutils literal notranslate"><spanclass="pre">location</span></code>).</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">exits</span></code> - this returns all objects inside this object that are <em>Exits</em>, that is, has the <codeclass="docutils literal notranslate"><spanclass="pre">destination</span></code> property set.</p></li>
</ul>
<p>The last two properties are special:</p>
<ulclass="simple">
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">cmdset</span></code> - this is a handler that stores all <aclass="reference external"href="/Commands.html#Command_Sets">command sets</a> defined on the object (if any).</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">scripts</span></code> - this is a handler that manages <aclass="reference internal"href="Scripts.html"><spanclass="doc">Scripts</span></a> attached to the object (if any).</p></li>
</ul>
<p>The Object also has a host of useful utility functions. See the function headers in <codeclass="docutils literal notranslate"><spanclass="pre">src/objects/objects.py</span></code> for their arguments and more details.</p>
<ulclass="simple">
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">msg()</span></code> - this function is used to send messages from the server to an account connected to this object.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">msg_contents()</span></code> - calls <codeclass="docutils literal notranslate"><spanclass="pre">msg</span></code> on all objects inside this object.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">search()</span></code> - 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 <codeclass="docutils literal notranslate"><spanclass="pre">caller</span></code> and one can do <codeclass="docutils literal notranslate"><spanclass="pre">caller.search()</span></code> to find objects in the room to operate on).</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">execute_cmd()</span></code> - Lets the object execute the given string as if it was given on the command line.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">move_to</span></code> - 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.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">clear_exits()</span></code> - will delete all <aclass="reference external"href="/Objects.html#Exits">Exits</a> to <em>and</em> from this object.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">clear_contents()</span></code> - this will not delete anything, but rather move all contents (except Exits) to their designated <codeclass="docutils literal notranslate"><spanclass="pre">Home</span></code> locations.</p></li>
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">delete()</span></code> - deletes this object, first calling <codeclass="docutils literal notranslate"><spanclass="pre">clear_exits()</span></code> and
<p>The Object Typeclass defines many more <em>hook methods</em> beyond <codeclass="docutils literal notranslate"><spanclass="pre">at_object_creation</span></code>. 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 <codeclass="docutils literal notranslate"><spanclass="pre">evennia.objects.objects</span></code> for an updated list of all the available hooks or the <aclass="reference external"href="api/evennia.objects.objects.html#defaultobject">API for DefaultObject here</a>.</p>
</div>
<divclass="section"id="subclasses-of-object">
<h2>Subclasses of <codeclass="docutils literal notranslate"><spanclass="pre">Object</span></code><aclass="headerlink"href="#subclasses-of-object"title="Permalink to this headline">¶</a></h2>
<p>There are three special subclasses of <em>Object</em> in default Evennia - <em>Characters</em>, <em>Rooms</em> and <em>Exits</em>. 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.</p>
<divclass="section"id="characters">
<h3>Characters<aclass="headerlink"href="#characters"title="Permalink to this headline">¶</a></h3>
<p>Characters are objects controlled by <aclass="reference internal"href="Accounts.html"><spanclass="doc">Accounts</span></a>. When a new Account
logs in to Evennia for the first time, a new <codeclass="docutils literal notranslate"><spanclass="pre">Character</span></code> object is created and
the Account object is assigned to the <codeclass="docutils literal notranslate"><spanclass="pre">account</span></code> attribute. A <codeclass="docutils literal notranslate"><spanclass="pre">Character</span></code> object
must have a <aclass="reference external"href="/Commands.html#Command_Sets">Default Commandset</a> set on itself at
creation, or the account will not be able to issue any commands! If you just
inherit your own class from <codeclass="docutils literal notranslate"><spanclass="pre">evennia.DefaultCharacter</span></code> and make sure to use
<codeclass="docutils literal notranslate"><spanclass="pre">super()</span></code> to call the parent methods you should be fine. In
<codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/characters.py</span></code> is an empty <codeclass="docutils literal notranslate"><spanclass="pre">Character</span></code> class ready for you
to modify.</p>
</div>
<divclass="section"id="rooms">
<h3>Rooms<aclass="headerlink"href="#rooms"title="Permalink to this headline">¶</a></h3>
<p><em>Rooms</em> are the root containers of all other objects. The only thing really separating a room from any other object is that they have no <codeclass="docutils literal notranslate"><spanclass="pre">location</span></code> of their own and that default commands like <codeclass="docutils literal notranslate"><spanclass="pre">@dig</span></code> creates objects of this class - so if you want to expand your rooms with more functionality, just inherit from <codeclass="docutils literal notranslate"><spanclass="pre">ev.DefaultRoom</span></code>. In <codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/rooms.py</span></code> is an empty <codeclass="docutils literal notranslate"><spanclass="pre">Room</span></code> class ready for you to modify.</p>
</div>
<divclass="section"id="exits">
<h3>Exits<aclass="headerlink"href="#exits"title="Permalink to this headline">¶</a></h3>
<p><em>Exits</em> are objects connecting other objects (usually <em>Rooms</em>) together. An object named <em>North</em> or <em>in</em> might be an exit, as well as <em>door</em>, <em>portal</em> or <em>jump out the window</em>. An exit has two things that separate them from other objects. Firstly, their <em>destination</em> 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 <aclass="reference internal"href="Commands.html"><spanclass="doc">Transit Command</span></a> 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 <em>destination</em> - this allows you to just enter the name of the exit on its own to move around, just as you would expect.</p>
<p>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 <aclass="reference internal"href="Locks.html"><spanclass="doc">locked</span></a> using an access_type called <em>traverse</em> and also make use of a few hook methods for giving feedback if the traversal fails. See <codeclass="docutils literal notranslate"><spanclass="pre">evennia.DefaultExit</span></code> for more info. In <codeclass="docutils literal notranslate"><spanclass="pre">mygame/typeclasses/exits.py</span></code> there is an empty <codeclass="docutils literal notranslate"><spanclass="pre">Exit</span></code> class for you to modify.</p>
<p>The process of traversing an exit is as follows:</p>
<olclass="simple">
<li><p>The traversing <codeclass="docutils literal notranslate"><spanclass="pre">obj</span></code> sends a command that matches the Exit-command name on the Exit object. The <aclass="reference internal"href="Commands.html"><spanclass="doc">cmdhandler</span></a> detects this and triggers the command defined on the Exit. Traversal always involves the “source” (the current location) and the <codeclass="docutils literal notranslate"><spanclass="pre">destination</span></code> (this is stored on the Exit object).</p></li>
<li><p>The Exit command checks the <codeclass="docutils literal notranslate"><spanclass="pre">traverse</span></code> lock on the Exit object</p></li>
<li><p>The Exit command triggers <codeclass="docutils literal notranslate"><spanclass="pre">at_traverse(obj,</span><spanclass="pre">destination)</span></code> on the Exit object.</p></li>
<li><p>In <codeclass="docutils literal notranslate"><spanclass="pre">at_traverse</span></code>, <codeclass="docutils literal notranslate"><spanclass="pre">object.move_to(destination)</span></code> is triggered. This triggers the following hooks, in order:</p>
<olclass="simple">
<li><p><codeclass="docutils literal notranslate"><spanclass="pre">obj.at_before_move(destination)</span></code> - if this returns False, move is aborted.</p></li>
<li><p>Move is performed by changing <codeclass="docutils literal notranslate"><spanclass="pre">obj.location</span></code> from source location to <codeclass="docutils literal notranslate"><spanclass="pre">destination</span></code>.</p></li>
<li><p>On the Exit object, <codeclass="docutils literal notranslate"><spanclass="pre">at_after_traverse(obj,</span><spanclass="pre">source)</span></code> is triggered.</p></li>
</ol>
<p>If the move fails for whatever reason, the Exit will look for an Attribute <codeclass="docutils literal notranslate"><spanclass="pre">err_traverse</span></code> on itself and display this as an error message. If this is not found, the Exit will instead call
<codeclass="docutils literal notranslate"><spanclass="pre">at_failed_traverse(obj)</span></code> on itself.</p>
