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<h3><a href="../index.html">Table of Contents</a></h3>
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<li><a class="reference internal" href="#">Building a train that moves</a><ul>
<li><a class="reference internal" href="#creating-our-train-object">Creating our train object</a></li>
<li><a class="reference internal" href="#entering-and-leaving-the-train">Entering and leaving the train</a></li>
<li><a class="reference internal" href="#locking-down-the-commands">Locking down the commands</a></li>
<li><a class="reference internal" href="#making-our-train-move">Making our train move</a></li>
<li><a class="reference internal" href="#adding-in-scripts">Adding in scripts</a></li>
<li><a class="reference internal" href="#expanding">Expanding</a></li>
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<section class="tex2jax_ignore mathjax_ignore" id="building-a-train-that-moves">
<h1>Building a train that moves<a class="headerlink" href="#building-a-train-that-moves" title="Permalink to this headline"></a></h1>
<blockquote>
<div><p>TODO: This should be updated for latest Evennia use.</p>
</div></blockquote>
<p>Vehicles are things that you can enter and then move around in your game world. Here we’ll explain how to create a train, but this can be equally applied to create other kind of vehicles
(cars, planes, boats, spaceships, submarines, …).</p>
<p>Objects in Evennia have an interesting property: you can put any object inside another object. This is most obvious in rooms: a room in Evennia is just like any other game object (except rooms tend to not themselves be inside anything else).</p>
<p>Our train will be similar: it will be an object that other objects can get inside. We then simply
move the Train, which brings along everyone inside it.</p>
<section id="creating-our-train-object">
<h2>Creating our train object<a class="headerlink" href="#creating-our-train-object" title="Permalink to this headline"></a></h2>
<p>The first step we need to do is create our train object, including a new typeclass. To do this,
create a new file, for instance in <code class="docutils literal notranslate"><span class="pre">mygame/typeclasses/train.py</span></code> with the following content:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># in mygame/typeclasses/train.py</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">DefaultObject</span>
<span class="k">class</span> <span class="nc">TrainObject</span><span class="p">(</span><span class="n">DefaultObject</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_object_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c1"># We&#39;ll add in code here later.</span>
<span class="k">pass</span>
</pre></div>
</div>
<p>Now we can create our train in our game:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">create</span><span class="o">/</span><span class="n">drop</span> <span class="n">train</span><span class="p">:</span><span class="n">train</span><span class="o">.</span><span class="n">TrainObject</span>
</pre></div>
</div>
<p>Now this is just an object that doesn’t do much yet… but we can already force our way inside it
and back (assuming we created it in limbo).</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">tel</span> <span class="n">train</span>
<span class="n">tel</span> <span class="n">limbo</span>
</pre></div>
</div>
</section>
<section id="entering-and-leaving-the-train">
<h2>Entering and leaving the train<a class="headerlink" href="#entering-and-leaving-the-train" title="Permalink to this headline"></a></h2>
<p>Using the <code class="docutils literal notranslate"><span class="pre">tel</span></code>command like shown above is obviously not what we want. <code class="docutils literal notranslate"><span class="pre">&#64;tel</span></code> is an admin command and normal players will thus never be able to enter the train!</p>
<p>It is also not really a good idea to use <span class="xref myst">Exits</span> to get in and out of the train - Exits are (at least by default) objects too. They point to a specific destination. If we put an Exit in this room leading inside the train it would stay here when the train moved away (still leading into the train like a magic portal!). In the same way, if we put an Exit object inside the train, it would always point back to this room, regardless of where the Train has moved.</p>
<p>Now, one <em>could</em> define custom Exit types that move with the train or change their destination in the right way - but this seems to be a pretty cumbersome solution.</p>
<p>What we will do instead is to create some new <a class="reference internal" href="../Components/Commands.html"><span class="doc std std-doc">commands</span></a>: one for entering the train and
another for leaving it again. These will be stored <em>on the train object</em> and will thus be made
available to whomever is either inside it or in the same room as the train.</p>
<p>Let’s create a new command module as <code class="docutils literal notranslate"><span class="pre">mygame/commands/train.py</span></code>:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># mygame/commands/train.py</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">Command</span><span class="p">,</span> <span class="n">CmdSet</span>
<span class="k">class</span> <span class="nc">CmdEnterTrain</span><span class="p">(</span><span class="n">Command</span><span class="p">):</span>
<span class="w"> </span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd"> entering the train</span>
<span class="sd"> </span>
<span class="sd"> Usage:</span>
<span class="sd"> enter train</span>
<span class="sd"> This will be available to players in the same location</span>
<span class="sd"> as the train and allows them to embark. </span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;enter train&quot;</span>
<span class="k">def</span> <span class="nf">func</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">train</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">obj</span>
<span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You board the train.&quot;</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">move_to</span><span class="p">(</span><span class="n">train</span><span class="p">,</span> <span class="n">move_type</span><span class="o">=</span><span class="s2">&quot;board&quot;</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">CmdLeaveTrain</span><span class="p">(</span><span class="n">Command</span><span class="p">):</span>
<span class="w"> </span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd"> leaving the train </span>
<span class="sd"> </span>
<span class="sd"> Usage:</span>
<span class="sd"> leave train</span>
<span class="sd"> This will be available to everyone inside the </span>
<span class="sd"> train. It allows them to exit to the train&#39;s</span>
<span class="sd"> current location. </span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;leave train&quot;</span>
<span class="k">def</span> <span class="nf">func</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">train</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">obj</span>
<span class="n">parent</span> <span class="o">=</span> <span class="n">train</span><span class="o">.</span><span class="n">location</span>
<span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">move_to</span><span class="p">(</span><span class="n">parent</span><span class="p">,</span> <span class="n">move_type</span><span class="o">=</span><span class="s2">&quot;disembark&quot;</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">CmdSetTrain</span><span class="p">(</span><span class="n">CmdSet</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_cmdset_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">CmdEnterTrain</span><span class="p">())</span>
<span class="bp">self</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">CmdLeaveTrain</span><span class="p">())</span>
</pre></div>
</div>
<p>Note that while this seems like a lot of text, the majority of lines here are taken up by
documentation.</p>
<p>These commands are work in a pretty straightforward way: <code class="docutils literal notranslate"><span class="pre">CmdEnterTrain</span></code> moves the location of the player to inside the train and <code class="docutils literal notranslate"><span class="pre">CmdLeaveTrain</span></code> does the opposite: it moves the player back to the
current location of the train (back outside to its current location). We stacked them in a <a class="reference internal" href="../Components/Command-Sets.html"><span class="doc std std-doc">cmdset</span></a> <code class="docutils literal notranslate"><span class="pre">CmdSetTrain</span></code> so they can be used.</p>
<p>To make the commands work we need to add this cmdset to our train typeclass:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># file mygame/typeclasses/train.py</span>
<span class="kn">from</span> <span class="nn">commands.train</span> <span class="kn">import</span> <span class="n">CmdSetTrain</span>
<span class="kn">from</span> <span class="nn">typeclasses.objects</span> <span class="kn">import</span> <span class="n">Object</span>
<span class="k">class</span> <span class="nc">TrainObject</span><span class="p">(</span><span class="n">Object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_object_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cmdset</span><span class="o">.</span><span class="n">add_default</span><span class="p">(</span><span class="n">CmdSetTrain</span><span class="p">)</span>
</pre></div>
</div>
<p>If we now <code class="docutils literal notranslate"><span class="pre">reload</span></code> our game and reset our train, those commands should work and we can now enter and leave the train:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">reload</span>
<span class="n">typeclass</span><span class="o">/</span><span class="n">force</span><span class="o">/</span><span class="n">reset</span> <span class="n">train</span> <span class="o">=</span> <span class="n">train</span><span class="o">.</span><span class="n">TrainObject</span>
<span class="n">enter</span> <span class="n">train</span>
<span class="n">leave</span> <span class="n">train</span>
</pre></div>
</div>
<p>Note the switches used with the <code class="docutils literal notranslate"><span class="pre">typeclass</span></code> command: The <code class="docutils literal notranslate"><span class="pre">/force</span></code> switch is necessary to assign our object the same typeclass we already have. The <code class="docutils literal notranslate"><span class="pre">/reset</span></code> re-triggers the typeclass’ <code class="docutils literal notranslate"><span class="pre">at_object_creation()</span></code> hook (which is otherwise only called the very first an instance is created).
As seen above, when this hook is called on our train, our new cmdset will be loaded.</p>
</section>
<section id="locking-down-the-commands">
<h2>Locking down the commands<a class="headerlink" href="#locking-down-the-commands" title="Permalink to this headline"></a></h2>
<p>If you have played around a bit, you’ve probably figured out that you can use <code class="docutils literal notranslate"><span class="pre">leave</span> <span class="pre">train</span></code> when
outside the train and <code class="docutils literal notranslate"><span class="pre">enter</span> <span class="pre">train</span></code> when inside. This doesn’t make any sense … so let’s go ahead
and fix that. We need to tell Evennia that you can not enter the train when you’re already inside
or leave the train when you’re outside. One solution to this is <a class="reference internal" href="../Components/Locks.html"><span class="doc std std-doc">locks</span></a>: we will lock down the commands so that they can only be called if the player is at the correct location.</p>
<p>Since we didn’t set a <code class="docutils literal notranslate"><span class="pre">lock</span></code> property on the Command, it defaults to <code class="docutils literal notranslate"><span class="pre">cmd:all()</span></code>. This means that everyone can use the command as long as they are in the same room <em>or inside the train</em>.</p>
<p>First of all we need to create a new lock function. Evennia comes with many lock functions built-in
already, but none that we can use for locking a command in this particular case. Create a new entry in <code class="docutils literal notranslate"><span class="pre">mygame/server/conf/lockfuncs.py</span></code>:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span>
<span class="c1"># file mygame/server/conf/lockfuncs.py</span>
<span class="k">def</span> <span class="nf">cmdinside</span><span class="p">(</span><span class="n">accessing_obj</span><span class="p">,</span> <span class="n">accessed_obj</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="w"> </span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd"> Usage: cmdinside() </span>
<span class="sd"> Used to lock commands and only allows access if the command</span>
<span class="sd"> is defined on an object which accessing_obj is inside of. </span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="k">return</span> <span class="n">accessed_obj</span><span class="o">.</span><span class="n">obj</span> <span class="o">==</span> <span class="n">accessing_obj</span><span class="o">.</span><span class="n">location</span>
</pre></div>
</div>
<p>If you didn’t know, Evennia is by default set up to use all functions in this module as lock
functions (there is a setting variable that points to it).</p>
<p>Our new lock function, <code class="docutils literal notranslate"><span class="pre">cmdinside</span></code>, is to be used by Commands. The <code class="docutils literal notranslate"><span class="pre">accessed_obj</span></code> is the Command object (in our case this will be <code class="docutils literal notranslate"><span class="pre">CmdEnterTrain</span></code> and <code class="docutils literal notranslate"><span class="pre">CmdLeaveTrain</span></code>) — Every command has an <code class="docutils literal notranslate"><span class="pre">obj</span></code> property: this is the the object on which the command “sits”. Since we added those commands to our train object, the <code class="docutils literal notranslate"><span class="pre">.obj</span></code> property will be set to the train object. Conversely, <code class="docutils literal notranslate"><span class="pre">accessing_obj</span></code> is the object that called the command: in our case it’s the Character trying to enter or leave the train.</p>
<p>What this function does is to check that the player’s location is the same as the train object. If
it is, it means the player is inside the train. Otherwise it means the player is somewhere else and
the check will fail.</p>
<p>The next step is to actually use this new lock function to create a lock of type <code class="docutils literal notranslate"><span class="pre">cmd</span></code>:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># file commands/train.py</span>
<span class="o">...</span>
<span class="k">class</span> <span class="nc">CmdEnterTrain</span><span class="p">(</span><span class="n">Command</span><span class="p">):</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;enter train&quot;</span>
<span class="n">locks</span> <span class="o">=</span> <span class="s2">&quot;cmd:not cmdinside()&quot;</span>
<span class="c1"># ...</span>
<span class="k">class</span> <span class="nc">CmdLeaveTrain</span><span class="p">(</span><span class="n">Command</span><span class="p">):</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;leave train&quot;</span>
<span class="n">locks</span> <span class="o">=</span> <span class="s2">&quot;cmd:cmdinside()&quot;</span>
<span class="c1"># ...</span>
</pre></div>
</div>
<p>Notice how we use the <code class="docutils literal notranslate"><span class="pre">not</span></code> here so that we can use the same <code class="docutils literal notranslate"><span class="pre">cmdinside</span></code> to check if we are inside
and outside, without having to create two separate lock functions. After a <code class="docutils literal notranslate"><span class="pre">&#64;reload</span></code> our commands
should be locked down appropriately and you should only be able to use them at the right places.</p>
<blockquote>
<div><p>Note: If you’re logged in as the super user (user <code class="docutils literal notranslate"><span class="pre">#1</span></code>) then this lock will not work: the super
user ignores lock functions. In order to use this functionality you need to <code class="docutils literal notranslate"><span class="pre">&#64;quell</span></code> first.</p>
</div></blockquote>
</section>
<section id="making-our-train-move">
<h2>Making our train move<a class="headerlink" href="#making-our-train-move" title="Permalink to this headline"></a></h2>
<p>Now that we can enter and leave the train correctly, it’s time to make it move. There are different
things we need to consider for this:</p>
<ul class="simple">
<li><p>Who can control your vehicle? The first player to enter it, only players that have a certain “drive” skill, automatically?</p></li>
<li><p>Where should it go? Can the player steer the vehicle to go somewhere else or will it always follow the same route?</p></li>
</ul>
<p>For our example train we’re going to go with automatic movement through a predefined route (its track). The train will stop for a bit at the start and end of the route to allow players to enter and leave it.</p>
<p>Go ahead and create some rooms for our train. Make a list of the room ids along the route (using the <code class="docutils literal notranslate"><span class="pre">xe</span></code> command).</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">&gt;</span> <span class="n">dig</span><span class="o">/</span><span class="n">tel</span> <span class="n">South</span> <span class="n">station</span>
<span class="o">&gt;</span> <span class="n">ex</span> <span class="c1"># note the id of the station</span>
<span class="o">&gt;</span> <span class="n">tunnel</span><span class="o">/</span><span class="n">tel</span> <span class="n">n</span> <span class="o">=</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span>
<span class="o">&gt;</span> <span class="n">ex</span> <span class="c1"># note the id of the track</span>
<span class="o">&gt;</span> <span class="n">tunnel</span><span class="o">/</span><span class="n">tel</span> <span class="n">n</span> <span class="o">=</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span>
<span class="o">&gt;</span> <span class="o">...</span>
<span class="o">&gt;</span> <span class="n">tunnel</span><span class="o">/</span><span class="n">tel</span> <span class="n">n</span> <span class="o">=</span> <span class="n">North</span> <span class="n">Station</span>
</pre></div>
</div>
<p>Put the train onto the tracks:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">tel</span> <span class="n">south</span> <span class="n">station</span>
<span class="n">tel</span> <span class="n">train</span> <span class="o">=</span> <span class="n">here</span>
</pre></div>
</div>
<p>Next we will tell the train how to move and which route to take.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># file typeclasses/train.py</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">DefaultObject</span><span class="p">,</span> <span class="n">search_object</span>
<span class="kn">from</span> <span class="nn">commands.train</span> <span class="kn">import</span> <span class="n">CmdSetTrain</span>
<span class="k">class</span> <span class="nc">TrainObject</span><span class="p">(</span><span class="n">DefaultObject</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_object_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cmdset</span><span class="o">.</span><span class="n">add_default</span><span class="p">(</span><span class="n">CmdSetTrain</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">driving</span> <span class="o">=</span> <span class="kc">False</span>
<span class="c1"># The direction our train is driving (1 for forward, -1 for backwards)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">direction</span> <span class="o">=</span> <span class="mi">1</span>
<span class="c1"># The rooms our train will pass through (change to fit your game)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">rooms</span> <span class="o">=</span> <span class="p">[</span><span class="s2">&quot;#2&quot;</span><span class="p">,</span> <span class="s2">&quot;#47&quot;</span><span class="p">,</span> <span class="s2">&quot;#50&quot;</span><span class="p">,</span> <span class="s2">&quot;#53&quot;</span><span class="p">,</span> <span class="s2">&quot;#56&quot;</span><span class="p">,</span> <span class="s2">&quot;#59&quot;</span><span class="p">]</span>
<span class="k">def</span> <span class="nf">start_driving</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">driving</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">def</span> <span class="nf">stop_driving</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">driving</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">def</span> <span class="nf">goto_next_room</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">currentroom</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">location</span><span class="o">.</span><span class="n">dbref</span>
<span class="n">idx</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">rooms</span><span class="o">.</span><span class="n">index</span><span class="p">(</span><span class="n">currentroom</span><span class="p">)</span> <span class="o">+</span> <span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">direction</span>
<span class="k">if</span> <span class="n">idx</span> <span class="o">&lt;</span> <span class="mi">0</span> <span class="ow">or</span> <span class="n">idx</span> <span class="o">&gt;=</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">rooms</span><span class="p">):</span>
<span class="c1"># We reached the end of our path</span>
<span class="bp">self</span><span class="o">.</span><span class="n">stop_driving</span><span class="p">()</span>
<span class="c1"># Reverse the direction of the train</span>
<span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">direction</span> <span class="o">*=</span> <span class="o">-</span><span class="mi">1</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">roomref</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">rooms</span><span class="p">[</span><span class="n">idx</span><span class="p">]</span>
<span class="n">room</span> <span class="o">=</span> <span class="n">search_object</span><span class="p">(</span><span class="n">roomref</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">move_to</span><span class="p">(</span><span class="n">room</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">msg_contents</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;The train is moving forward to </span><span class="si">{</span><span class="n">room</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">.&quot;</span><span class="p">)</span>
</pre></div>
</div>
<p>We added a lot of code here. Since we changed the <code class="docutils literal notranslate"><span class="pre">at_object_creation</span></code> to add in variables we will have to reset our train object like earlier (using the <code class="docutils literal notranslate"><span class="pre">&#64;typeclass/force/reset</span></code> command).</p>
<p>We are keeping track of a few different things now: whether the train is moving or standing still,
which direction the train is heading to and what rooms the train will pass through.</p>
<p>We also added some methods: one to start moving the train, another to stop and a third that actually moves the train to the next room in the list. Or makes it stop driving if it reaches the last stop.</p>
<p>Let’s try it out, using <code class="docutils literal notranslate"><span class="pre">py</span></code> to call the new train functionality:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">&gt;</span> <span class="n">reload</span>
<span class="o">&gt;</span> <span class="n">typeclass</span><span class="o">/</span><span class="n">force</span><span class="o">/</span><span class="n">reset</span> <span class="n">train</span> <span class="o">=</span> <span class="n">train</span><span class="o">.</span><span class="n">TrainObject</span>
<span class="o">&gt;</span> <span class="n">enter</span> <span class="n">train</span>
<span class="o">&gt;</span> <span class="n">py</span> <span class="n">here</span><span class="o">.</span><span class="n">goto_next_room</span><span class="p">()</span>
</pre></div>
</div>
<p>You should see the train moving forward one step along the rail road.</p>
</section>
<section id="adding-in-scripts">
<h2>Adding in scripts<a class="headerlink" href="#adding-in-scripts" title="Permalink to this headline"></a></h2>
<p>If we wanted full control of the train we could now just add a command to step it along the track when desired. We want the train to move on its own though, without us having to force it by manually calling the <code class="docutils literal notranslate"><span class="pre">goto_next_room</span></code> method.</p>
<p>To do this we will create two <a class="reference internal" href="../Components/Scripts.html"><span class="doc std std-doc">scripts</span></a>: one script that runs when the train has stopped at
a station and is responsible for starting the train again after a while. The other script will take
care of the driving.</p>
<p>Let’s make a new file in <code class="docutils literal notranslate"><span class="pre">mygame/typeclasses/trainscript.py</span></code></p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># file mygame/typeclasses/trainscript.py</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">DefaultScript</span>
<span class="k">class</span> <span class="nc">TrainStoppedScript</span><span class="p">(</span><span class="n">DefaultScript</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_script_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;trainstopped&quot;</span>
<span class="bp">self</span><span class="o">.</span><span class="n">interval</span> <span class="o">=</span> <span class="mi">30</span>
<span class="bp">self</span><span class="o">.</span><span class="n">persistent</span> <span class="o">=</span> <span class="kc">True</span>
<span class="bp">self</span><span class="o">.</span><span class="n">repeats</span> <span class="o">=</span> <span class="mi">1</span>
<span class="bp">self</span><span class="o">.</span><span class="n">start_delay</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">def</span> <span class="nf">at_repeat</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">start_driving</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">at_stop</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">scripts</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">TrainDrivingScript</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">TrainDrivingScript</span><span class="p">(</span><span class="n">DefaultScript</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_script_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;traindriving&quot;</span>
<span class="bp">self</span><span class="o">.</span><span class="n">interval</span> <span class="o">=</span> <span class="mi">1</span>
<span class="bp">self</span><span class="o">.</span><span class="n">persistent</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">def</span> <span class="nf">is_valid</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">driving</span>
<span class="k">def</span> <span class="nf">at_repeat</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">driving</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="k">else</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">goto_next_room</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">at_stop</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">obj</span><span class="o">.</span><span class="n">scripts</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">TrainStoppedScript</span><span class="p">)</span>
</pre></div>
</div>
<p>Those scripts work as a state system: when the train is stopped, it waits for 30 seconds and then
starts again. When the train is driving, it moves to the next room every second. The train is always
in one of those two states - both scripts take care of adding the other one once they are done.</p>
<p>As a last step we need to link the stopped-state script to our train, reload the game and reset our
train again., and we’re ready to ride it around!</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># file typeclasses/train.py</span>
<span class="kn">from</span> <span class="nn">typeclasses.trainscript</span> <span class="kn">import</span> <span class="n">TrainStoppedScript</span>
<span class="k">class</span> <span class="nc">TrainObject</span><span class="p">(</span><span class="n">DefaultObject</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">at_object_creation</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c1"># ...</span>
<span class="bp">self</span><span class="o">.</span><span class="n">scripts</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">TrainStoppedScript</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">&gt;</span> <span class="n">reload</span>
<span class="o">&gt;</span> <span class="n">typeclass</span><span class="o">/</span><span class="n">force</span><span class="o">/</span><span class="n">reset</span> <span class="n">train</span> <span class="o">=</span> <span class="n">train</span><span class="o">.</span><span class="n">TrainObject</span>
<span class="o">&gt;</span> <span class="n">enter</span> <span class="n">train</span>
<span class="c1"># output:</span>
<span class="o">&lt;</span> <span class="n">The</span> <span class="n">train</span> <span class="ow">is</span> <span class="n">moving</span> <span class="n">forward</span> <span class="n">to</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span><span class="o">.</span>
<span class="o">&lt;</span> <span class="n">The</span> <span class="n">train</span> <span class="ow">is</span> <span class="n">moving</span> <span class="n">forward</span> <span class="n">to</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span><span class="o">.</span>
<span class="o">&lt;</span> <span class="n">The</span> <span class="n">train</span> <span class="ow">is</span> <span class="n">moving</span> <span class="n">forward</span> <span class="n">to</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span><span class="o">.</span>
<span class="o">...</span>
<span class="o">&lt;</span> <span class="n">The</span> <span class="n">train</span> <span class="ow">is</span> <span class="n">moving</span> <span class="n">forward</span> <span class="n">to</span> <span class="n">Following</span> <span class="n">a</span> <span class="n">railroad</span><span class="o">.</span>
<span class="o">&lt;</span> <span class="n">The</span> <span class="n">train</span> <span class="ow">is</span> <span class="n">moving</span> <span class="n">forward</span> <span class="n">to</span> <span class="n">North</span> <span class="n">station</span><span class="o">.</span>
<span class="n">leave</span> <span class="n">train</span>
</pre></div>
</div>
<p>Our train will stop 30 seconds at each end station and then turn around to go back to the other end.</p>
</section>
<section id="expanding">
<h2>Expanding<a class="headerlink" href="#expanding" title="Permalink to this headline"></a></h2>
<p>This train is very basic and still has some flaws. Some more things to do:</p>
<ul class="simple">
<li><p>Make it look like a train.</p></li>
<li><p>Make it impossible to exit and enter the train mid-ride. This could be made by having the enter/exit commands check so the train is not moving before allowing the caller to proceed.</p></li>
<li><p>Have train conductor commands that can override the automatic start/stop.</p></li>
<li><p>Allow for in-between stops between the start- and end station</p></li>
<li><p>Have a rail road track instead of hard-coding the rooms in the train object. This could for example be a custom <span class="xref myst">Exit</span> only traversable by trains. The train will follow the track. Some track segments can split to lead to two different rooms and a player can switch the direction to which room it goes.</p></li>
<li><p>Create another kind of vehicle!</p></li>
</ul>
</section>
</section>
</div>
</div>
</div>
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