Question

I am trying to return an object method on the event jQuery.change() of a text field,
here is the code:

var Utente = function(indice){

    this.Indice = indice;
    this.Dati = new Array();

    this.initialize = function() {
        this.Dati['stato_civile'] = this.getField('stato_civile').val();
        this.onChange('stato_civile',this.checkObbligatorieta);
    }

    this.getField = function(name) {
        return $('#'+indice+name);
    }

    this.onChange = function(field, func) {

        this.getField(field).live('change',function() {
            return func.apply(); 
        });

    }

    this.checkObbligatorieta = function() {

         this.Dati['stato_civile'] = this.getField('stato_civile').val();

         [...]

    }

    this.initialize();

}

Using this I get the field "#stato_civile" returns the function this.checkObbligatorieta correctly but it gives me an error:
** this.getField('stato_civile').val() is not a function

I think it’s something strictly related with the scope, but I can’t figure it out.

Answer 1

That’s because you’re not invoking func() in the same context as the caller, so this is not bound to the same object.

You can fix the problem by passing this to apply():

this.onChange = function(field, func) {
    this.getField(field).live("change", function() {
        return func.apply(this);
    });
};