Knockout - how to update an computed observableArray before using its value in some function

Question

I have one computed observableArray that is bound directly to some radio button and one event bound to that radio button selection. The radio button selection adds some value to array also the selection triggers event where I use the array value.

The problem I am facing is that the array is getting updated(via computed logic) after event function is executed but I have to check the array content(primarily length) in the event function itself. If I use the function as it is now, I am getting the older value. Is there a way that I can force the array to update the values ( evaluate computed value) before I can use it in the event function?

<input type="radio" data-bind="attr: {name: name}, checked: val, event :{ change: $parent.Changed }" value="No" />

//    Knockout code
this.Items = ko.computed(function () {
    //Add selected items to ItemsArray
}
this.Changed = function () {
    if (self.Items().length > 2) {
        //Do sth
    }
}

Please post some code (maybe a repro in JSFiddle), without seeing your code it is very hard to tell what are you trying to achieve/ask here. — nemesv, Jun 18 '13 at 15:44
See the possible duplicate- you can call `myObservable.valueHasMutated()` to notify subscribers that they should update. — Jacob Krall, Jun 18 '13 at 15:45
@JacobKrall I did not valueHasMutated function for observableArrays. Can you point me to the right direction? — aaa, Jun 18 '13 at 15:47
@JacobKrall hasValueMutated just works for observables, not for computed!!! — aaa, Jun 19 '13 at 06:45

score 1 · Answer 1 · answered Jun 19 '13 at 06:02

Instead of having a computed observable and change event binding you can subscribe to the observable that is bound to the checked property. In the subscribed function you can calculate Items array at first and then do your length check:

this.val.subscribe(function (newVal) {
    // update Items array
    ...

    //
    if (self.Items().length > 2) {
        ...
    }
});

Knockout - how to update an computed observableArray before using its value in some function

1 Answers1