Problem with OO programming in javascript and ASP.NET AJAX

Question

Hi,

I'm trying to keep as much OO as possible, but ASP.NET AJAX seems to be doing something strange after returning from the server...

function Person( personId ) {
var id = personId;
var firstName;
var lastName;

this.initializeStep1 = function() {
    PeopleServices.getFirstName(id, this.initializeStep2);
}

this.initializeStep2 = function(foundFirstName) {
    alert(foundFirstName);
    firstName = foundFirstName;
    PeopleServices.getLastName(id, this.initializeStep3);
}

this.initializeStep3 = function(foundLastName) {
    alert(foundLastName);
    alert(firstName);
    lastName= foundLastName;
} 

this.initializeStep1();

}

This is the basis of it. So basically it is creating a person and retrieving their first and last name from the server in order to initialize the person.

When I create a new person, it goes through initializeStep1, calls the server webmethod getFirstName, and eventually reaches initializeStep2. the alert(foundFirstName); works, it alerts the name that was found and it is correct... now after setting the private variable firstName to what was found, I make a second call to the server...

This time, it does not reach initializeStep3, and I know it shouldn't have failed on the server end because even if I replace the line

PeopleServices.getLastName(id, this.initializeStep3);

with

PeopleServices.getFirstName(id, this.initializeStep3);

it still does not work.

I was wondering if after the first server call it lost the reference to "this" or something similar to that happened where I cannot call initializeStep3 the way I am. Anyone have any ideas?

some notes:

• I know the server webmethods are all working, I've tested them individually.
• I'm not sure if my OO is right here.
• I'm not sure if I'm going about AJAX right either.

Thanks for your help!

Answer 1

You need a closure

var that = this;
PeopleServices.getFirstName(id, function (x) { 
                                    that.initializeStep3(x);
                                } 
);