Knockout - Using foreach and sort together
The observableArray.sort
returns the sorted underlying ("regular") array and not a observableArray
that is why the changes not shown on the UI.
To have the sorting and the UI updated you need to create a ko.computed
which does the sorting and use the computed in your binding. Because the ko.computed
will listen on the widgets
changes and recalculate the sorting.
var widgets= ko.observableArray();
var sortedWidgets = ko.computed(function() {
return widgets().sort(function (left, right) {
return left.order() == right.order() ?
0 :
(left.order() < right.order() ? -1 : 1);
});
});
Then you can bind it with:
<article data-bind="foreach: sortedWidgets" />
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rbrtl
Experienced software anaylyst/developer running a small team developing mainly web based and mobile software. Main technologies used are C#, Objective C, Java, MS SQL Server, Visual Studio, ASP.Net MVC, JQuery, Javascript, WPF, WCF, breezejs, durandal and angularjs
Updated on June 19, 2020Comments
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rbrtl about 4 years
I am having trouble combining the foreach binding with a sort. I have a list bound like so:
<article data-bind="foreach: widgets">
Widgets is a simple obvservable array:
var widgets= ko.observableArray();
This works nicely giving me a list of my "widgets". If I add a new "widget" to this list then it appears dynamically in the list via data binding.
However as soon as I add sorting to the array:
<article data-bind="foreach: widgets.sort(function (left, right) { return left.order() == right.order() ? 0 : (left.order() < right.order() ? -1 : 1); })">
Then newly added widgets no longer appear in my list - unless I reload the page. (The sorting works nicely at this point - if I update the "order" field that I am sorting on then the items in my list are dynamically re-sorted).
How can I go about getting the sorting to play nicely with the dynamic updating of new items in my observable array?
I am using Breezejs in order to retrieve my data, however I do not think that is impacting on this scenario.
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rbrtl about 11 yearsThank- you - that worked nicely. Can you please update your answer to include "function () " at the start of the ko.computed (inside the first parentheses). I will then accept it as the answer.
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rbrtl about 11 yearsFurther to your answer above, how do I then make this work for a nested foreach i.e. a foreach on a navigation property of one of the widgets in my top level list. In this case I do not explicitly declare the observable array that I am binding to so I cannot see how to use this approach.
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nemesv about 11 yearsI've fixed the typo in my answer. I'm not familiar with Breezejs but I think it can be configured to create these custom sorted properties for you. Anyway JS is dynamic so you can add new properties to any already existing object.
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rbrtl about 11 yearsI was able to get the sorting to work on the nested foreach for the navigation properties by adding a knockout computed property to my Breeze entity in a custom constructor - see breezejs.com/documentation/extending-entities.
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PW Kad about 11 years@daveywc Could you post an example of how you were able to that while using sort?