root/trunk/jsondatasource.js

// this is a datasource abstract base class which will retreive
// data from a server endpoint with JSON

// takes URL, data updated callback, options
// options.noFetch == don't automatically retrieve data when initialized
JSONDataSource = new Class (DataSource, {

  init: function (endPoint, dataUpdatedCallback, opts) {
    JSONDataSource.superClass.init.apply(this, []);
    this.endPoint = endPoint;
    this.dataUpdatedCallback = dataUpdatedCallback;
    this.currentOperationCallback = null;

    if (opts && opts.method)
        this.method = opts.method;

    if (opts && opts.data)
        this.reqData = opts.data;

    if (opts && opts.onError) {
        this.onError = opts.onError;
    } else {
        this.onError = this.defaultErrorHandler;
    }

    if (!opts || !opts["noFetch"])
      this.getData();

    this.hourglass = null;
  },

  update: function (opts) {
    opts = opts ? opts : {};
    var hourglassOnWidget = opts["hourglassOnWidget"];
    var callback = opts["callback"];
    if (callback)
      this.currentOperationCallback = callback;

    if (hourglassOnWidget) {
      this.hourglass = new Hourglass();
      this.hourglass.init(hourglassOnWidget);
    }
    this.getData();
  },

  receivedData: function (data) {
    this.theData = data;
    this.callWatchers();

    if (this.dataUpdatedCallback)
      this.dataUpdatedCallback(data);

    if (this.hourglass) {
      this.hourglass.hide();
      this.hourglass = null;
    }

    if (this.currentOperationCallback)
      this.currentOperationCallback(data);
  },

  getData: function () {
    var reqOpts = {};
    reqOpts.onError = this.onError.bind(this);
    reqOpts.url = this.endPoint;
    reqOpts.onData = this.receivedData.bind(this);

    if (this.reqData)
        reqOpts.data = this.reqData;

    if (this.method)
        reqOpts.method = this.method;

    HTTPReq.getJSON(reqOpts);
  },

  defaultErrorHandler: function (err) {
    alert("Error: " + err);
  }
});