Reactive async pattern

README.md

Example usage:

Template.xyz.value = function () {
  return ReactiveAsync("Template_xyz_value", function (w) {
  	someAsyncFunction(function (result) {
  		w.set(result);
  		w.done();
  	});
  }, {initial: ""});
};

package.js

Package.describe({
  summary: "Reactive async pattern helper"
});

Package.on_use(function (api) {
  api.use([
    "deps",
    "underscore"
  ], "client");

  api.add_files([
    "reactive-async.js"
  ], "client");

  api.export("ReactiveAsync");
});

reactive-async.js

var store = {};

ReactiveAsync = function (uniqueId, workspace, options) {
  uniqueId = uniqueId + (Deps.currentComputation && Deps.currentComputation._id);

  var opts = _.extend({
    initial: undefined
  }, options);

  if (!_.has(store, uniqueId)) {
    store[uniqueId] = {
      dep: new Deps.Dependency,
      state: "idle",
      val: opts.initial,
      newVal: opts.initial
    };
  }

  var o = store[uniqueId];

  o.dep.depend();

  if (o.state === "idle") {
    o.state = "working";
    o.newVal = opts.initial;

    _.isFunction(workspace) && workspace({
      done: function () {
        o.state = "done";
        this.flush();
      },
      get: function () {
        return o.newVal;
      },
      set: function (setVal) {
        o.newVal = setVal;
      },
      getCurrent: function () {
        return o.val;
      },
      flush: function () {
        o.val = o.newVal;
        o.dep.changed();
      }
    });
  }

  if (o.state === "done") {
    o.state = "idle";
  }

  return o.val;
};