KnockoutJS : initial values are not posted to server when using ko.toJSON(this)? - forms

Question

I've this javascript viewmodel defined:
function PersonViewModel() {
// Data members
this.Name = ko.observable();
this.Function_Id = ko.observable();
this.SubFunction_Id = ko.observable();
this.Functions = ko.observableArray();
this.SubFunctions = ko.observableArray();
// Whenever the Function changes, update the SubFunctions selection
this.Function_Id.subscribe(function (id) {
this.GetSubFunctions(id);
}, this);
// Functions to get data from server
this.Init = function () {
this.GetFunctions();
this.Function_Id('#(Model.Function_Id)');
};
this.GetFunctions = function () {
var vm = this;
$.getJSON(
'#Url.Action("GetFunctions", "Function")',
function (data) {
vm.Functions(data);
}
);
};
this.GetSubFunctions = function (Function_Id) {
var vm = this;
if (Function_Id != null) {
$.getJSON(
'#Url.Action("GetSubFunctions", "Function")',
{ Function_Id: Function_Id },
function (data) {
vm.SubFunctions(data);
}
);
}
else {
vm.SubFunction_Id(0);
vm.SubFunctions([]);
}
};
this.Save = function () {
var PostData = ko.toJSON(this);
var d = $.dump(PostData);
alert(d);
$.ajax({
type: 'POST',
url: '/Person/Save',
data: PostData,
contentType: 'application/json',
success: function (data) {
alert(data);
}
});
};
}
$(document).ready(function () {
var personViewModel = new PersonViewModel();
personViewModel.Init();
ko.applyBindings(personViewModel);
});
When the Submit button is clicked, the data from the select lists is posted, but NOT the 'Function_Id'.
When I choose a different value in the Function dropdown list, and the click the Submit button, the value for 'Function_Id' is correctly posted.
How to fix this ?

Answer 1

It's because the scope of the this keyword in javascript
this.Init = function () {
this.GetFunctions(); // this === PersonViewModel.Init
this.Function_Id('#(Model.Function_Id)'); // calls PersonViewModel.Init.Function_Id(...)
};
You should store the refrence to the PersonViewModel instance.
var self = this;
self.Init = function () {
self.GetFunctions();
self.Function_Id('#(Model.Function_Id)'); // calls PersonViewModel.Function_Id(...)
};