lifecycle.html

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  <h1>Lifecycle</h1>

  <p>Tyranid supports a lifecycle for its models to help model data workflows and lifecycle within Tyranid models.</p>

  <h2><u>boot</u></h2>

  <p>Initialization code should be placed in the collection <a href="component#boot"><u><i>Component.</i>boot</u></a>.</p>

  <p>Any sort of code that needs to run when the application servers are first launched should be placed here.</p>

  <p>The Tyranid bootstrapping framework also supports dealing with complex bootstrapping dependencies and
  orderings -- including circular dependencies.</p>

  <h2>Events</h2>

  <p><a href="event">Events</a> are the primary place to handle most lifecycle and workflow concerns.</p>

  <p><b>On-change handlers</b> provide a place to do additional tasks when documents are created
  or modified.  For example, updating ElasticSearch indices, updating permissions, creation of related
  documents, and so on.</p>

  <p><b>On-remove handlers</b> provide a place to perform any tasks that are needed when a document is removed.  For example,
  removing documents from external indices, removing dependent documents, and so on.</p>



  <h2>Validation</h2>

  <p>In addition to standard built-in validations like <u>required</u>, <u>minlength</u>, and so on (see
  <a href="field#def">field definitions</a> for a full list), <a href="field"><u>Field</u></a>s can have
  also an (optionally asynchronous) handler defined for each field.  This can be used to perform field-level
  validations that are triggered while interacting with a client-side form.</p>
  
  <p>For example, the following validation could be provided which front-end controls would invoke when a user
  focuses out of an email field:</p>

<pre><code class="js">      <i>...,</i>
      email: {
        is: 'email',
        required: true,
        async validate() {
          if (this.email) {
            return (
              (await User.exists({
                query: {
                  email: {
                    $regex: '^' + escapeRegex(this.email) + '$',
                    $options: 'i'
                  },
                  _id: { $ne: this._id }
                }
              })) && `Sorry, that email is already used: ${this.email}`
            );
          }
        }
      },
      <i>...</i></code></pre>

  <h2><u><i>Collection.</i>fromClient</u></h2>

  <p>Implementing a collection <a href="collection#def"><u><i>Collection.</i>fromClient</u></a> handler
  provides the primary place to perform updates to collection instances after being created or edited
  on the client.</p>

  <p>It can also be used as a place to provide additional security checks and verifications as all updates from client
  will go through this method before being committed to the database.</p>

  <p>This method handler can optionally be <u>async</u> so that security checks and other asynchronous code can be called.</p>
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