If your application is hosted on App Engine, a cloud storage service isavailable that allows users to save, load, share, and publish their programs.

Setting up App Engine

The first objective is to get your own copy of Blockly running on App Engine.

1. Download and install the Python SDK.
2. Log into Google App Engine and create an application.
3. Edit appengine/app.yaml and change the application ID from blockly-demo to the application name you created in the previous step.
4. Copy (or soft-link) the following files and directories into appengine/static/:
   • demos/
   • msg/
   • media/
   • *_compressed.js
5. Optional: If you'd like to use blockly_uncompressed.js on the server, also copy that file into appengine/static/, copy core into appengine/static/, and copy closure-library/ into the parent directory, appengine/.
6. Optional: If you'd like to run the Blockly Playground, you'll have to copy the blocks, generators, and tests directories, as well as the files in step 5.
7. Run the Google App Engine Launcher from the GUI, add your appengine directory as an existing application, and press the "Deploy" button. If you prefer to use the command line, run: appcfg.py --oauth2 update appengine/.

Once Blockly is uploaded you can point a browser to the URL you created in step 2. You should see a list of demos, including the cloud storage demo.

Talking to the Cloud

Examine the source of the storage demoat demos/storage/index.htmland note the following features.First, there is a script include that loads the cloud storage API:

<script src="/storage.js"></script>

Note that this script assumes there is only one Blockly workspace on the page.There are also these message definitions, which you should modify as desired:

BlocklyStorage.HTTPREQUEST_ERROR = 'There was a problem with the request.\n';
BlocklyStorage.LINK_ALERT = 'Share your blocks with this link:\n\n%1';
BlocklyStorage.HASH_ERROR = 'Sorry, "%1" doesn\'t correspond with any saved Blockly file.';
BlocklyStorage.XML_ERROR = 'Could not load your saved file.\n' +
    'Perhaps it was created with a different version of Blockly?';

Translations of these messages into other languages can be found in Blockly Games inthe json directory.

Saving the current blocks is a single call to BlocklyStorage.link():

<button onclick="BlocklyStorage.link()">Save Blocks</button>

To restore saved blocks on page load, just call BlocklyStorage.retrieveXml with the URL's hash after Blockly has been injected:

if ('BlocklyStorage' in window && window.location.hash.length > 1) {
  BlocklyStorage.retrieveXml(window.location.hash.substring(1));
}

Local Storage

The storage.js API also offers the ability to save a single set of blocks inthe browser's local storage. This may be implemented instead of cloud storage,or in addition with cloud storage (though in the latter case one has to becareful of both types of storage attempting to restore at once).

To restore blocks from local storage, call BlocklyStorage.restoreBlocks in atimeout right after Blockly has been injected.

window.setTimeout(BlocklyStorage.restoreBlocks, 0);

To automatically backup the blocks into local storage when the user leaves thepage, call BlocklyStorage.backupOnUnload and it will register an eventlistener on the page's unload event.

BlocklyStorage.backupOnUnload();

Example

Here isa live demoof cloud storage.