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<li><a class="reference internal" href="#">Command Cooldown</a><ul>
<li><a class="reference internal" href="#non-persistent-cooldown">Non-persistent cooldown</a></li>
<li><a class="reference internal" href="#persistent-cooldown">Persistent cooldown</a></li>
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<div class="section" id="command-cooldown">
<h1>Command Cooldown<a class="headerlink" href="#command-cooldown" title="Permalink to this headline"></a></h1>
<p>Some types of games want to limit how often a command can be run. If a
character casts the spell <em>Firestorm</em>, you might not want them to spam that
command over and over. Or in an advanced combat system, a massive swing may
offer a chance of lots of damage at the cost of not being able to re-do it for
a while. Such effects are called <em>cooldowns</em>.</p>
<p>This page exemplifies a very resource-efficient way to do cooldowns. A more
active way is to use asynchronous delays as in the <a class="reference external" href="/Command-Duration.html#Blocking-Commands">command duration
tutorial</a>, the two might be useful to
combine if you want to echo some message to the user after the cooldown ends.</p>
<div class="section" id="non-persistent-cooldown">
<h2>Non-persistent cooldown<a class="headerlink" href="#non-persistent-cooldown" title="Permalink to this headline"></a></h2>
<p>This little recipe will limit how often a particular command can be run. Since
Commands are class instances, and those are cached in memory, a command
instance will remember things you store on it. So just store the current time
of execution! Next time the command is run, it just needs to check if it has
that time stored, and compare it with the current time to see if a desired
delay has passed.</p>
<div class="highlight-python notranslate"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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31</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">time</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">default_cmds</span>
<span class="k">class</span> <span class="nc">CmdSpellFirestorm</span><span class="p">(</span><span class="n">default_cmds</span><span class="o">.</span><span class="n">MuxCommand</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="sd"> Spell - Firestorm</span>
<span class="sd"> Usage: </span>
<span class="sd"> cast firestorm &lt;target&gt;</span>
<span class="sd"> </span>
<span class="sd"> This will unleash a storm of flame. You can only release one </span>
<span class="sd"> firestorm every five minutes (assuming you have the mana). </span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;cast firestorm&quot;</span>
<span class="n">locks</span> <span class="o">=</span> <span class="s2">&quot;cmd:isFireMage()&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="s2">&quot;Implement the spell&quot;</span>
<span class="c1"># check cooldown (5 minute cooldown)</span>
<span class="n">now</span> <span class="o">=</span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()</span>
<span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="s2">&quot;lastcast&quot;</span><span class="p">)</span> <span class="ow">and</span> \
<span class="n">now</span> <span class="o">-</span> <span class="bp">self</span><span class="o">.</span><span class="n">lastcast</span> <span class="o">&lt;</span> <span class="mi">5</span> <span class="o">*</span> <span class="mi">60</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="s2">&quot;You cannot cast this spell again yet.&quot;</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="n">message</span><span class="p">)</span>
<span class="k">return</span>
<span class="c1">#[the spell effect is implemented]</span>
<span class="c1"># if the spell was successfully cast, store the casting time</span>
<span class="bp">self</span><span class="o">.</span><span class="n">lastcast</span> <span class="o">=</span> <span class="n">now</span>
</pre></div>
</td></tr></table></div>
<p>We just check the <code class="docutils literal notranslate"><span class="pre">lastcast</span></code> flag, and update it if everything works out.
Simple and very effective since everything is just stored in memory. The
drawback of this simple scheme is that its non-persistent. If you do
<code class="docutils literal notranslate"><span class="pre">&#64;reload</span></code>, the cache is cleaned and all such ongoing cooldowns will be
forgotten. It is also limited only to this one command, other commands cannot
(easily) check for this value.</p>
</div>
<div class="section" id="persistent-cooldown">
<h2>Persistent cooldown<a class="headerlink" href="#persistent-cooldown" title="Permalink to this headline"></a></h2>
<p>This is essentially the same mechanism as the simple one above, except we use
the database to store the information which means the cooldown will survive a
server reload/reboot. Since commands themselves have no representation in the
database, you need to use the caster for the storage.</p>
<div class="highlight-python notranslate"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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16</pre></div></td><td class="code"><div class="highlight"><pre><span></span> <span class="c1"># inside the func() of CmdSpellFirestorm as above</span>
<span class="c1"># check cooldown (5 minute cooldown)</span>
<span class="n">now</span> <span class="o">=</span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()</span>
<span class="n">lastcast</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">firestorm_lastcast</span>
<span class="k">if</span> <span class="n">lastcast</span> <span class="ow">and</span> <span class="n">now</span> <span class="o">-</span> <span class="n">lastcast</span> <span class="o">&lt;</span> <span class="mi">5</span> <span class="o">*</span> <span class="mi">60</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="s2">&quot;You need to wait before casting this spell again.&quot;</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="n">message</span><span class="p">)</span>
<span class="k">return</span>
<span class="c1">#[the spell effect is implemented]</span>
<span class="c1"># if the spell was successfully cast, store the casting time</span>
<span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">db</span><span class="o">.</span><span class="n">firestorm_lastcast</span> <span class="o">=</span> <span class="n">now</span>
</pre></div>
</td></tr></table></div>
<p>Since we are storing as an <a class="reference internal" href="Attributes.html"><span class="doc">Attribute</span></a>, we need to identify the
variable as <code class="docutils literal notranslate"><span class="pre">firestorm_lastcast</span></code> so we are sure we get the right one (well
likely have other skills with cooldowns after all). But this method of
using cooldowns also has the advantage of working <em>between</em> commands - you can
for example let all fire-related spells check the same cooldown to make sure
the casting of <em>Firestorm</em> blocks all fire-related spells for a while. Or, in
the case of taking that big swing with the sword, this could now block all
other types of attacks for a while before the warrior can recover.</p>
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