forked from mirrors/gecko-dev
795e20a3a6
MozReview-Commit-ID: EwcE881XGfp --HG-- extra : rebase_source : 70283e30375019e56c355dd61c92352b31481228
50 lines
2 KiB
ReStructuredText
50 lines
2 KiB
ReStructuredText
.. _lifecycle:
|
|
|
|
Managing the Extension Lifecycle
|
|
================================
|
|
The techniques described in previous pages allow a WebExtension API to
|
|
be loaded and instantiated only when an extension that uses the API is
|
|
activated.
|
|
But there are a few other events in the extension lifecycle that an API
|
|
may need to respond to.
|
|
|
|
Extension Shutdown
|
|
------------------
|
|
APIs that allocate any resources (e.g., adding elements to the browser's
|
|
user interface, setting up internal event listeners, etc.) must free
|
|
these resources when the extension for which they are allocated is
|
|
shut down. An API does this by using the ``callOnClose()``
|
|
method on an `Extension <reference.html#extension-class>`_ object.
|
|
|
|
Extension Uninstall and Update
|
|
------------------------------
|
|
In addition to resources allocated within an individual browser session,
|
|
some APIs make durable changes such as setting preferences or storing
|
|
data in the user's profile.
|
|
These changes are typically not reverted when an extension is shut down,
|
|
but when the extension is completely uninstalled (or stops using the API).
|
|
To handle this, extensions can be notified when an extension is uninstalled
|
|
or updated. Extension updates are a subtle case -- consider an API that
|
|
makes some durable change based on the presence of a manifest property.
|
|
If an extension uses the manifest key in one version and then is updated
|
|
to a new version that no longer uses the manifest key,
|
|
the ``onManifestEntry()`` method for the API is no longer called,
|
|
but an API can examine the new manifest after an update to detect that
|
|
the key has been removed.
|
|
|
|
To be notified of update and uninstall events, an extension lists these
|
|
events in the API manifest:
|
|
|
|
.. code-block:: json
|
|
|
|
"myapi": {
|
|
"schema": "...",
|
|
"url": "...",
|
|
"events": ["update", "uninstall"]
|
|
}
|
|
|
|
If these properties are present, the ``onUpdate()`` and ``onUninstall()``
|
|
methods will be called for the relevant ``ExtensionAPI`` instances when
|
|
an extension that uses the API is updated or uninstalled.
|
|
|
|
.. Should we even document onStartup()? I think no...
|