Upgrading

ctrl.js

// ctrl.js
//   origin: http://example.com
//   scope: "/*"
 
"use strict";

// Called when this controller is installed as the newest version
// for a scope. Perhaps a clearer name for what is now sketched
// as "onupdate". Note that this is called BEFORE "onupgrade" is
// sent to a previous version's controller.
this.oninstall = function(e) {
  // We start with empty caches for each version of each controller.
  assert(!this.caches.get("main"));

  var main = new Cache([
    // A resource used in v1. As an optimization, the browser 
    //can keep the copy it downloaded from v1 and avoid the network 
    // hit, assuming it hasn't expired in the HTTP cache sense.
    "http://cdn.com/js/lib.js",
    // A resource that's new to v2. This will be fetched now.
    "/app/2/app.js",
    // ...
  ]);
  this.caches.set("main", main);
};

// Called when the controller is replaced by a newer 
// version, but after the new version's oninstall has returned.
this.onupgrade = function(e) {
  // We could free resources here, but in most cases won't need 
  // to. Instead, when the last live page controlled by our 
  // replaced controller is unloaded, the browser can remove 
  // all caches "owned" by the now-removed controller. Assuming
  // that v3 also defines a "main", its "oninstall" will not be 
  // able to see the "main" cache associated with v2. It can, 
  // however, define a new one and, thanks to the overlapping 
  // resources optimization outlined above, avoid re-fetching most 
  // of the resources it needs.
};