title: Fluid-Alias-View-Helper with result of another view helper
body: <p>In one of my NEOS Templates I try to solve the simple task of generating a random number (within a specified range) and store it into a variable for later usage.</p>
  
  <p>Since none of the default view helpers offers such a feature I developed my own view helper, which expects a min and max value. Internally the view helper uses php's <code>rand($min, $max)</code>.</p>
  
  <p>The following example is working in my template:</p>
  
  <pre><code>site:RandomNumber(0, 17)
  </code></pre>
  
  <p>As expected this outputs a random number. However now I need to store the result into a variable, since I have to use it more than one time.</p>
  
  <p>I came across <em>fluids alias</em>-view-helper:</p>
  
  <pre><code>&lt;f:alias map="{number: 33}"&gt;
      The number is {number}
  &lt;/f:alias&gt;
  </code></pre>
  
  <p>This results in:</p>
  
  <pre><code>The number is 33
  </code></pre>
  
  <p>Now I want the number not to be 33, but the result of my <code>RandomNumber</code>-view-helper.</p>
  
  <p>I tried things like:</p>
  
  <pre><code>&lt;f:alias map="{number: {site:RandomNumber(0, 17)}}"&gt;
      The number is {number}
  &lt;/f:alias&gt;
  </code></pre>
  
  <p>This however throws an Exception saying:</p>
  
  <pre><code>The argument "map" was registered with type "array", but is of type "string" 
  in view helper "TYPO3\Fluid\ViewHelpers\AliasViewHelper"
  </code></pre>
  
  <p>The docs of the <code>f:alias</code>view-helper say accepted values are other view-helpers, but they never give any examples on that.</p>
  
  <p>Am I completely wrong with this approach? Is it simply not possible to assign a simple variable within a fluid-template?</p>
  
  <p><strong>Further information:</strong>
  I do have a slider on the website, which should start with a different slide on (almost) every page-load. So I need to grab this random slide-number, which I have to refer to in the slider markup several times.</p>