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                    isRxCollection()
            
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                    Insert
            
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                    Find
            
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                    Functions
            
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                    get()
            
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                    get$()
            
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                    proxy-get
            
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                    update()
            
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                    atomicUpdate()
            
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                    atomicPatch()
            
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                    $
            
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                    remove()
            
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                    deleted$
            
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                    toJSON()
            
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                    set()
            
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                    save()
            
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                    isRxDocument()
            
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                    RxQuery
            
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                    find()
            
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                    findOne()
            
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                    exec()
            
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                    $
            
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                    update()
            
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                    remove()
            
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                    doesDocumentDataMatch()
            
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                    Specific Index
            
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                    Examples
            
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                    isRxQuery()
            
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                    RxAttachment
            
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                    Middleware-hooks
            
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                    ORM/DRM
            
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                    Population
            
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                    Encryption
            
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                                <h1 id="middleware">Middleware</h1>
<p>RxDB supports middleware-hooks like <a href="http://mongoosejs.com/docs/middleware.html" target="_blank">mongoose</a>.
Middleware (also called pre and post hooks) are functions which are passed control during execution of asynchronous functions.
The hooks are specified on RxCollection-level and help to create a clear what-happens-when-structure of your code.</p>
<p>Hooks can be defined to run parallel or as series one after another.
Hooks can be synchronous or asynchronous when they return a Promise.
To stop the operation at a specific hook, throw an error.</p>
<h2 id="list">List</h2>
<p>RxDB supports the following hooks:</p>
<ul>
<li>preInsert</li>
<li>postInsert</li>
<li>preSave</li>
<li>postSave</li>
<li>preRemove</li>
<li>postRemove</li>
<li>postCreate</li>
</ul>
<h3 id="why-is-there-no-validate-hook">Why is there no validate-hook?</h3>
<p>Different to mongoose, the validation on document-data is running on the field-level for every change to a document.
This means if you set the value <code>lastName</code> of a RxDocument, then the validation will only run on the changed field, not the whole document.
Therefore it is not useful to have validate-hooks when a document is written to the database.</p>
<h2 id="use-cases">Use Cases</h2>
<p>Middleware are useful for atomizing model logic and avoiding nested blocks of async code.
Here are some other ideas:</p>
<ul>
<li>complex validation</li>
<li>removing dependent documents</li>
<li>asynchronous defaults</li>
<li>asynchronous tasks that a certain action triggers</li>
<li>triggering custom events</li>
<li>notifications</li>
</ul>
<h2 id="usage">Usage</h2>
<p>All hooks have the plain data as first parameter, and all but <code>preInsert</code> also have the <code>RxDocument</code>-instance as second parameter. If you want to modify the data in the hook, change attributes of the first parameter.</p>
<p>All hook functions are also <code>this</code>-bind to the <code>RxCollection</code>-instance.</p>
<h3 id="insert">Insert</h3>
<p>An insert-hook receives the data-object of the new document.</p>
<h4 id="lifecycle">lifecycle</h4>
<ul>
<li>RxCollection.insert is called</li>
<li>preInsert series-hooks</li>
<li>preInsert parallel-hooks</li>
<li>schema validation runs</li>
<li>new document is written to database</li>
<li>postInsert series-hooks</li>
<li>postInsert parallel-hooks</li>
<li>event is emitted to RxDatabase and RxCollection</li>
</ul>
<h4 id="preinsert">preInsert</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.preInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData</span>)</span>{
    <span class="hljs-comment">// set age to 50 before saving</span>
    plainData.age = <span class="hljs-number">50</span>;
}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.preInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.preInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// stop the insert-operation</span>
myCollection.preInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData</span>)</span>{
  <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">&apos;stop&apos;</span>);
}, <span class="hljs-literal">false</span>);
</code></pre>
<h4 id="postinsert">postInsert</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.postInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.postInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.postInsert(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);
</code></pre>
<h3 id="save">Save</h3>
<p>A save-hook receives the document which is saved.</p>
<h4 id="lifecycle">lifecycle</h4>
<ul>
<li>RxDocument.save is called</li>
<li>preSave series-hooks</li>
<li>preSave parallel-hooks</li>
<li>updated document is written to database</li>
<li>postSave series-hooks</li>
<li>postSave parallel-hooks</li>
<li>event is emitted to RxDatabase and RxCollection</li>
</ul>
<h4 id="presave">preSave</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.preSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
    <span class="hljs-comment">// modify anyField before saving</span>
    plainData.anyField = <span class="hljs-string">&apos;anyValue&apos;</span>;
}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.preSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.preSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// stop the save-operation</span>
myCollection.preSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">&apos;stop&apos;</span>);
}, <span class="hljs-literal">false</span>);
</code></pre>
<h4 id="postsave">postSave</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.postSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.postSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.postSave(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);
</code></pre>
<h3 id="remove">Remove</h3>
<p>An remove-hook receives the document which is removed.</p>
<h4 id="lifecycle">lifecycle</h4>
<ul>
<li>RxDocument.remove is called</li>
<li>preRemove series-hooks</li>
<li>preRemove parallel-hooks</li>
<li>deleted document is written to database</li>
<li>postRemove series-hooks</li>
<li>postRemove parallel-hooks</li>
<li>event is emitted to RxDatabase and RxCollection</li>
</ul>
<h4 id="preremove">preRemove</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.preRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.preRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.preRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// stop the remove-operation</span>
myCollection.preRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">&apos;stop&apos;</span>);
}, <span class="hljs-literal">false</span>);
</code></pre>
<h4 id="postremove">postRemove</h4>
<pre><code class="lang-js"><span class="hljs-comment">// series</span>
myCollection.postRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">false</span>);

<span class="hljs-comment">// parallel</span>
myCollection.postRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{

}, <span class="hljs-literal">true</span>);

<span class="hljs-comment">// async</span>
myCollection.postRemove(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Promise</span>(res =&gt; setTimeout(res, <span class="hljs-number">100</span>));
}, <span class="hljs-literal">false</span>);
</code></pre>
<h3 id="postcreate">postCreate</h3>
<p>This hook is called whenever a <code>RxDocument</code> is constructed.
You can use <code>postCreate</code> to modify every RxDocument-instance of the collection.
This adds a flexible way to add specify behavior to every document. You can also use it to add custom getter/setter to documents. PostCreate-hooks cannot be <strong>asynchronous</strong>.</p>
<pre><code class="lang-js">myCollection.postCreate(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">plainData, rxDocument</span>)</span>{
    <span class="hljs-built_in">Object</span>.defineProperty(rxDocument, <span class="hljs-string">&apos;myField&apos;</span>, {
        get: () =&gt; <span class="hljs-string">&apos;foobar&apos;</span>,
    });
});

<span class="hljs-keyword">const</span> doc = <span class="hljs-keyword">await</span> myCollection.findOne().exec();

<span class="hljs-built_in">console</span>.log(doc.myField);
<span class="hljs-comment">// &apos;foobar&apos;</span>
</code></pre>
<p>Notice: This hook does not run on already created or cached documents. Make sure to add <code>postCreate</code>-hooks before interacting with the collection.</p>

                                
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