---
layout: docs
title: Task
edit_url: "https://github.com/nylas/N1/blob/master/src/flux/tasks/task.coffee"
---

<h2>Summary</h2>

<div class="markdown-from-sourecode">
  <p><p>Tasks represent individual changes to the datastore that
alter the local cache and need to be synced back to the server.</p>
<p>To create a new task, subclass Task and implement the following methods:</p>
<ul>
<li>performLocal:
Return a <a href='https://github.com/petkaantonov/bluebird/blob/master/API.md'>Promise</a> that does work immediately. Must resolve or the task
will be thrown out. Generally, you should optimistically update
the local cache here.</li>
<li>performRemote:
Do work that requires dependencies to have resolved and may need to be
tried multiple times to succeed in case of network issues.
performRemote must return a <a href='https://github.com/petkaantonov/bluebird/blob/master/API.md'>Promise</a>, and it should always resolve with
<code>Task.Status.Finished</code> or <code>Task.Status.Retry</code>. Rejections are considered
exception cases and are logged to our server.
Returning <code>Task.Status.Retry</code> will cause the <code>TaskQueue</code> to leave your task
on the queue and run it again later. You should only return <code>Task.Status.Retry</code>
if your task encountered a transient error (for example, a <code>0</code> but not a <code>400</code>).</li>
<li>shouldWaitForTask:
Tasks may be arbitrarily dependent on other tasks. To ensure that
<code>performRemote</code> is called at the right time, subclasses should implement
<code>shouldWaitForTask(other)</code>. For example, the <code>SendDraft</code> task is dependent
on the draft&#39;s files&#39; <code>UploadFile</code> tasks completing.</li>
</ul>
<p>Tasks may also implement <code>shouldDequeueOtherTask(other)</code>. Returning true
will cause the other event to be removed from the queue. This is useful in
offline mode especially, when the user might <code>Save</code>,<code>Save</code>,<code>Save</code>,<code>Save</code>,<code>Send</code>.
Each newly queued <code>Save</code> can cancel the (unstarted) save task in the queue.</p>
<p>Tasks that need to support undo/redo should implement <code>canBeUndone</code>, <code>isUndo</code>,
<code>createUndoTask</code>, and <code>createIdenticalTask</code>.</p>
</p>
</div>

<ul>
</ul>