Question

my viewmodel has two arrays (simplified version)

array_a = ko.observableArray(["a", "b", "c"]);
array_b = ko.observableArray(["Foo", "Bar", "Bash"]);

I want to iterate over one while binding to the value of another so I have this

<ul data-bind="foreach: array_a">
<li><input data-bind="value: array_b()[$index()]" type="text"></li>
</ul

this shows the value but doesn’t seem to update it when the input text is changed??

Answer 1

If you want to have update-able values in your array_b you need to wrap the values into observables (because ko bindings are one way if the binding source is not an ko.observable).

So this should work:

array_b: ko.observableArray([ko.observable("Foo"), 
                             ko.observable("Bar"), 
                             ko.observable("Bash")])

Se in action in this JsFiddle.