jQuery Deferred, trouble getting a value in a chain

Question

The result of buildMyUrl is always undefined in the calling function. I'm not sure what I'm doing wrong chaining these functions:

var buildMyUrl = function (callback)
{   
    var param;

    var addParams = function (domainUrl)
    {
        domainUrl += "page.aspx?";
        domainUrl += "Param1=";
    };

    $.when(self.buildDomainUrl()).then(addParams);
};

buildDomainUrl returns a JQuery promise and adding parameters works fine. Now I have a function that would like to use the result of buildMyUrl:

    var buildAPageUrl  = function ()
    {
        var dfd = $.Deferred();

        var addCalendarPage = function (domainUrl)
        {
             dfd.resolve(domainUrl += "/Calendar.aspx?");
        };

   // Here lies the problem (buildMyUrl is undefined)
        $.when(buildMyUrl()).then(addCalendarPage);

        return dfd.promise();
    }

@Kevin B. buildMyLoginUrl should just be buildMyUrl my mistake. — Jon Wells, May 17 '12 at 14:41
`buildMyURL` isn't returning a deferred object. It isn't returning anything. — Kevin B, May 17 '12 at 14:43
Thats my question, I have tried to get buildMyUrl to return a promise but I can't get it to work. I don't know what I do wrong — Jon Wells, May 17 '12 at 14:45
Your function literally isn't returning anything. try `return $.when(...).then(...);`. You have to instruct to it what should be returned. — Kevin B, May 17 '12 at 14:53
putting the return in front returns the when but not the then — Jon Wells, May 17 '12 at 14:55
the `then` isn't a deferred object. `then` is a method similar to `done` and `fail` that adds callbacks to a deferred object. `$.when` does infact return a deferred object. — Kevin B, May 17 '12 at 14:59

score 0 · Accepted Answer · answered May 18 '12 at 09:39

The following works based on Kevin B's comments:

var buildMyUrl = function (callback)
{   
    var dfd = $.Deferred();
    var param;

    var addParams = function (domainUrl)
    {
        domainUrl += "page.aspx?";
        domainUrl += "Param1=";
        dfd.resolve();
    };

    $.when(self.buildDomainUrl()).then(addParams);
    return dfd.promise();
};

jQuery Deferred, trouble getting a value in a chain

1 Answers1