Knockout-Contrib/Knockout-Validation

Validation on nested objects not working after changing whole object

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#398 opened on Jan 28, 2014

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help wanted

Description

Hi, I have a problem with validating nested objects. I have following view model:

      var ViewModel = function (first) {
           this.person = ko.observable(new Person(first));

           this.changePerson = function () {
               this.person(new Person("changed"));
           };
      };

      var Person = function (first) {
           this.firstName = ko.observable(first).extend({
                required: true
           });
      };

everything works as expected as long as I do not call changePerson function. After calling change if I have element with data-bind="person().firstName" validation messages will not show. Working example (http://jsfiddle.net/MDhUR/). I found a work round to this issue - if I use to bind to firstName everything works as expected (http://jsfiddle.net/seRr5/1/) .

regards.

Contributor guide

Tech stack
javascript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Knockout.js basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The issue is that when replacing an observable containing a nested object, validation rules on the nested properties are not re evaluated. Look at the ko.validation plugin's initialization and how it subscribes to observables. Check if the validation is tied to the observable instance rather than its value. A possible fix involves ensuring validation is re applied when the observable value changes to a new object. Review the two JSFiddle examples provided to understand the working vs. non working scenarios. The relevant code is likely in the plugin's subscription logic for nested validation.