javascript - Using Knockout and Breeze with Cascading Dropdowns -


so i've been @ , forth quite long time now, i'll point.

i creating application based on hottowel template, i'm using knockout, breeze, q etc. i'm using breeze query data server, , load data first select (as options). changes selectedmodel observable , subscription triggers ( subscription current "solution", have used data-bind etc same results). subscription takes new selectedmodel value , uses data second observable. query passes , results stored in modelproperties observable array, yet ui not update second select (it's empty). strange thing is, pressing ctrl + f5 (i tried 50 times in row) populates correctly, never on first load.

tldr; 2 selects, selected option of first 1 defines query options of second one. queries work, observables populated, first select populated, second never on first boot on following ctrl+f5.

here snippets regarding piece of application: viewmodel:

define(['services/logger', 'services/datacontext'], function (logger, datacontext) {     var models = ko.observablearray();     var modelproperties = ko.observablearray();     var selectedmodel = ko.observable();     var init = true;      function activate() {         logger.log('search view activated', null, 'search', true);         return datacontext.getmodels(models);     }      var sub = selectedmodel.subscribe(function (newvalue) {         return datacontext.getmodelproperties(modelproperties, newvalue);     });      var vm = {         activate: activate,         models: models,         selectedmodel: selectedmodel,         modelproperties: modelproperties,         title: 'search view'     };      return vm;

the view's code:

<!doctype html> <html xmlns="http://www.w3.org/1999/xhtml"> <head>     <title></title> </head> <body id="one">     <select id="entityselect" class ="entityselect" name="first"         data-bind="options: models, value: selectedmodel">     </select>     <select id="propertyselect" class ="propertyselect" data-bind=     'options:modelproperties'></select> </body> </html>

and methods in datacontext:

        var getmodels = function (modelsobservable) {         var query = entityquery.from('models');         return manager.executequery(query)             .then(querysucceeded)             .fail(queryfailed);          function querysucceeded(data) {             logger.log("query succeeded", true);             logger.log(data);             if (modelsobservable) {                 modelsobservable(data.results);             }             logger.log('retrieved [models] remote data source',                 data, true);         }         function queryfailed(data) {             logger.log(data.tostring(), data, true);         }     };      var getmodelproperties = function (propertiesobservable,modelname) {         var query = entityquery.from('modelproperties').withparameters({ name: modelname });         return manager.executequery(query)             .then(querysucceeded)             .fail(queryfailed);          function querysucceeded(data) {             logger.log("query succeeded", null, true);             logger.log(data);             if (propertiesobservable) {                 propertiesobservable(data.results);             }             logger.log('retrieved [properties] remote data source',                 data, true);         }         function queryfailed(data) {             logger.log(data.tostring(), data, true);         }     };

once again i'd point out queries pass, , observablearrays populated results (checked .peek() ).

here screenshots clarify problem: on first boot vs : http://i.imgur.com/8gd53yh.png

then, ctrl+f5 http://i.imgur.com/vzo8d70.png

i have tried pretty can think of, , googled came mind, no avail. appreciated! also, first post here apologize mistakes!

here few comments -

your view makes no sense. if using hottowel template there lot of mark-up not needed there, considering using durandal.js composition , additional mark-up hurting you.

if indeed loading 'subview' more or less should - 

<select id="entityselect" class ="entityselect" name="first" data-bind="options: models, value: selectedmodel"></select> <select id="propertyselect" class ="propertyselect" data-bind='options:modelproperties'></select>

next, if using cascading dropdowns have mentioned method before , suggest everyone. make second dependent on first ko.computed.

var models = ko.observablearray(); var modelproperties = ko.computed(function () {     var modelarr = ko.observablearray();     if (!selectedmodel()) { return modelarr; }     datacontext.getmodelproperties(modelarr, selectedmodel().then(function() { return modelarr(); }); });

now modelproperties null until select model, go out , properties of model.

it's important understand difference between function declarations using. var myfunc = function () {}; constructor function , evaluate on view model instantiation. function myfunc () {} standard function , wait until called before evaluating.


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