Friday, December 31, 2010

Cross Domain Issues on CouchDB and Sencha Touch

Two of the best parts of the CouchDB are the REST HTTP API and the JSON-based data structure which makes it an ideal database solution for JavaScript-based Mobile App(WebApp). While trying to use the JavaScript-based framework( likes Sencha Touch) to work with CouchDB, the first issue is always the cross-domain Ajax problem. The solution is to use JSONP, however,  the JSONP can only fulfill the "GET" part, the "POST" part has to be achieved by a "proxy" solution which against the original simplicity philosophy - JavaScript + CouchDB only! If this is a read-only App then we can live with it by using JSONP, if data write back is necessary then we have to figure out a better way! Fortunately, the PhoneGap offers the solution, since the html files under PhoneGap are called by webkit with the file://protocol, the security policy does not apply!

On the previous post - Thanksgiving Weekend Crash Course - Android, Sencha Touch, PhoneGap and CouchDB I used the JSONP(Ext.util.JSONP.request) as the example, since it can be debugged under Chrome(or Firefox) then port to the Android. To test the Ajax function(Ext.Ajax.request) I have changed the codes as following
function makeAjaxRequest() {            
    url: '',
    method: "GET",
    params: {},
    success: function(res, request) {
               if (res) {
                     result = Ext.util.JSON.decode(res.responseText);
                        arr = [];
                        for (i=0; i< result.rows.length; i++){
                          arr.push({id: result.rows[i].id, img: result.rows[i].img, game:  result.rows[i].game, lastName: result.rows[i].lastName, firstName: result.rows[i].firstName});
                    else {
                        alert('There was an error retrieving the data.');
                failure: function(res, request){
                 alert('Failed: ', res.responseText);
  Ext.onReady(function() {

and under CouchDB a new "list" named "basic" needs to be created to work with the Ajax call, this "basic" list function will generate a JSON object instead of a Javascript function codes -

Thanksgiving Weekend Crash Course - Android, Sencha Touch, PhoneGap and CouchDB

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