I am trying to use the visible knockout binding and index within a foreach to implement line by line editing. This is done by creating a display and modify div for each line and using visible binding to select between them. The problem is that the observable does not track between the modify and display divs.
I created this fiddle http://jsfiddle.net/rscidmore/YrsCj/57/
To see the problem, click modify on a line, edit the value and click save. You can see that you now have two values for the same observable.
Javascript:
var myViewModel = {
vals: ko.observableArray([
{label: 'first', item: 'one'},
{label: 'second', item: 'two'},
{label: 'third', item: 'three'}
]),
idx: ko.observable(-1)
};
ko.applyBindings(myViewModel);
HTML:
<body class='ui-widget'>
<div class='container'>
<!-- ko foreach: vals -->
<div class='label' data-bind="visible: $root.idx() == $index()">
<span class='lbl' data-bind="text: label"></span>:
<input type='text' data-bind="value: item">
<input type='button' value="save" data-bind="click: function()
{ $root.idx(-1);}" />
</div>
<div class='label' data-bind="visible: $root.idx() != $index()">
<span class='lbl' data-bind="text: label"></span>:
<span data-bind="text: item"></span>
<input type='button' value="modify" data-bind="click: function()
{ $root.idx($index());}" />
</div>
<!-- /ko -->
</div>
</body>
The ko.observableArray only tracks item addition and removal, and it won't track if one its items have changed.
Form the documenation:
Key point: An observableArray tracks which objects are in the array, not the state of those objects
So you need to have observable properties on the items in order to track their changes:
vals: ko.observableArray([
{label: 'first', item: ko.observable('one')},
{label: 'second', item: ko.observable('two')},
{label: 'third', item: ko.observable('three')}
]),