How to call a method between different objects in Javascript?

Question

I'm developing an application for mobile devices using the DHTMLX-touch framework, which is basically javascript.

I have a class A where this function is implemented:

A.prototype.initEventHandler = function(controller) {
    $$('btn_submit').attachEvent('onItemClick', controller.switchView($$('ui_ewmon_main')));
}

First implementation

the object controller is an instance of the class B, and the class B is the following:

function B() {     
    //back button management
    this.last_view=new Array();
    this.current_view=this.ewmon_view.getRoot();

    this.switchView = function(next) {
        this.last_view[this.last_view.length]=this.current_view;
        this.current_view=next;
        next.show();
    }
}

with firebug i get this error:

A.js:32Uncaught TypeError: Object # has no method 'switchView'

Second implementation

if I try to define switchView function as a prototype function:

function B() {     
    //back button management
    this.last_view=new Array();
    this.current_view=this.ewmon_view.getRoot();
}
B.prototype.switchView = function(next) {
    this.last_view[this.last_view.length]=this.current_view;
    this.current_view=next;
    next.show();
}

in this case I get the following error:

B.js:13Uncaught TypeError: Cannot read property 'length' of undefined

Can anyone help me?

Thanks in advance Danilo

im creating the Bobject in the constructor of A object as: this.b = new B(); anyway the Prusse's solution worked for me. Thanks for your help — ddelizia
– ddelizia, Commented Oct 21, 2011 at 14:02

Prusse · Accepted Answer · 2011-10-21 16:25:52Z

3

You are calling attachEvent with the return of controller.switchView($$('ui_ewmon_main')), to get the result you seen to want do:

A.prototype.initEventHandler = function(controller) {
    $$('btn_submit').attachEvent('onItemClick', function(){ controller.switchView($$('ui_ewmon_main')); });
}

Edit:

Looking at the code you posted I will expect this error to show up. From the line this.current_view=this.ewmon_view.getRoot(); one will guess this.current_view is always an object like the one returned by EWmonView.prototype.getRoot(rigth?), but this object don't have a method show.

But you call controller.switchView($$('ui_ewmon_main')); causing this.current_view to be whatever is $$('ui_ewmon_main'), keeping different object types in the array this.last_view and this.current_view is the source of the mistake.

A dirty fix will be:

if (this.current_view.show) {
    this.current_view.show();
} else{
    $$('ui_ewmon_main').show(); //or $$('ui_ewmon_login').show() can tell what you want =)
}

In the place of the occurrences of this.current_view.show(); in EWmonController. But rework the code and get this.current_view to have always the same kind of objects looks like better to me.

edited Oct 21, 2011 at 16:25

answered Oct 20, 2011 at 15:33

Prusse

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2 Comments

ddelizia Over a year ago

Thanks Prusse,the solution worked well. Now I added the back function in the initEventHandler method: $$('btn_back').attachEvent('onItemClick', function(){ controller.lastView(); }); and in the B object I added:

B.prototype.lastView = function() { 	this.current_view=this.last_view[this.last_view.length-1]; 	delete this.last_view[this.last_view.length-1]; 	this.current_view.show(); }

when I click on btn_submit I can switch the view (calling the method show()), but after, when I click on btn_back I get B.js:23Uncaught TypeError: Object #<Object> has no method 'show' Help please.

ddelizia Over a year ago

Hi Prusse, you can find the 2 classes at this address the A class and here the B class. Tjanks in advance

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