I am a newbee to knockout, I'm trying to move from the MVC ViewModel binding.
I have a complex model:
SearchStudentsModel which has 2 properties
Collection of Students (Subset of students)
Number of Students overall
Note that the length of the collection isn't equal to the number overall.
I need to implement a search functionality
Student will have all the regular properties plus IsActive indicator.
I use ul and li tags to data-bind the details.
The search screen should facilitate the user in marking the active flag with an indicator (on and off) and immediately data should be saved in the database.
All the examples I referred to talk about only one level of model. I have a SearchStudent model and within that I have a collection of students.
How should the binding be for this hierarchy of models?
I have refactored your jsFiddle. Hoping you can now understand knockoutJS better. It is not your whole page/Knockout, but I think with this snippet your problem can be solved.
the markup:
<button id="searchEmployees" type="button" data-bind="click: search">Search</button>
<li data-bind="foreach: Employees">
ID: <span data-bind="text: Id"></span><br/>
Name: <span data-bind="text: Name"></span><br/>
Active: <span data-bind="click: ToggleActivation, text: IsActive"></span> <-- click<br/>
</li>
<span data-bind="text: Employees().length"></span> of
<span data-bind="text: AllEmployees().length"></span>
the js/viewmodel
function Employee(id, name, isactive){
var self = this;
self.IsActive = ko.observable(isactive);
self.Id = ko.observable(id);
self.Name = ko.observable(name);
self.ToggleActivation = function () {
if(self.IsActive() === true)
self.IsActive(false);
else
self.IsActive(true);
};
}
var searchEmployeeViewModel = function () {
var self = this;
self.Employees = ko.observableArray([]);
self.AllEmployees = ko.observableArray([]);
self.search = function () {
//Ajax call to populate Employees - foreach on onsuccess
var employee1 = new Employee(2, "Jane Doe", true);
var employee2 = new Employee(3, "Kyle Doe", false);
var employee3 = new Employee(4, "Tyra Doe", false);
var employee = new Employee(1, "John Doe", true);
self.AllEmployees.push(employee);
self.AllEmployees.push(employee1);
self.AllEmployees.push(employee2);
self.AllEmployees.push(employee3);
self.Employees.push(employee);
}
}
$(document).ready(function () {
ko.applyBindings(new searchEmployeeViewModel());
});
or you can simply use my jsFiddle if you do not like reading my code here ;)
Related
I have a ViewModel which I am binding to view list item.
var MyViewModel = function() {
var self = this;
self.addItems = function(vm) {
vm.inventoryItems.push('New Item');
}
};
var myVM= new MyViewModel();
ko.applyBindings(myVM);
The view model has a property called inventoryItems (which is from a service).
I am bidning that to view using ,
<ul data-bind="foreach:inventoryItems">
<li>
<input class="form-control" type="text" data-bind="value: $data" />
</li>
</ul>
<div class="text-right">
<a data-bind="click: $parent.addItems">+ Add more</a>
</div>
Now, the items that are already in the collection , inventoryItems are getting rendered fine.
When I am adding a new item using, I can see the items being added via console, but the view is not getting updated!
self.addItems = function(vm) {
vm.inventoryItems.push('New Item');
}
The below code snippet will make your inventoryItems observable
var MyViewModel = function () {
var self = this;
self.inventoryItems = ko.observableArray();
self.addItems = function (vm) {
vm.inventories.push('New Item');
self.inventoryItems(vm.inventories);
}
};
var myVM = new MyViewModel();
ko.applyBindings(myVM);
I currently have a list of students and a list of classes in a school object. I would like each class object to be able to display a filtered list of students based on the class id property.
I have tried to access the parent object via custom binding but have not had any success.
Perhaps I am looking at the problem the wrong way? I have spent a couple days on this and whichever way I tackle it I always need to access a value on a parent object.
Are there any methods of accessing what I need? I am beginning to think that it is not possible to access a global style variable.
function School()
{
var self = this;
self.ClassVMs = ko.observableArray([]).indexed('Number');
self.ChildVMs = ko.observableArray([]).indexed('Number');
}
function ClassVM(classId, text)
{
var self = this;
self.Number = ko.observable();
self.Text = ko.observable(text);
self.ClassId = ko.observable(classId);
}
function ChildVM(classId, text)
{
var self = this;
self.Number = ko.observable();
self.ClassId = ko.observable(classId);
self.Text = ko.observable(text);
}
I have a Fiddle with my setup. Any and all guidance is appreciated. Thanks
You do not need global variables to solve this. Knockout has $root and $parent to step slightly outside of the scope you're in inside a foreach. In addition, if really needed, you can always make sure the view models get another type of view model as its dependency. In fact, if one view model has a list of sub view models it already has such a dependency.
What you need to think about is what your UI/UX is going to be like. Are you designing your view models to support a view where the user is "viewing" a student and enrolls him/her in classes? Or is the app user viewing a class and adding students one by one?
Here's a variant that shows a little bit of both:
function School(classes) {
var self = this;
self.classes = ko.observableArray(classes);
self.students = ko.observableArray([]);
self.enroll = function(child, someClass) {
if (self.students().indexOf(child) < 0) {
self.students.push(child);
}
if (someClass.students().indexOf(child) < 0) {
someClass.students.push(child);
}
};
self.enrollNewChild = function(someClass) {
if (!!someClass.childToBeEnrolled()) {
self.enroll(someClass.childToBeEnrolled(), someClass);
someClass.childToBeEnrolled(null);
}
};
self.enrollInClass = function(child) {
if (!!child.classToBeEnrolledIn()) {
self.enroll(child, child.classToBeEnrolledIn());
child.classToBeEnrolledIn(null);
}
};
}
function Class(id, txt) {
var self = this;
self.id = ko.observable(id);
self.txt = ko.observable(txt);
self.students = ko.observableArray([]);
self.studentsCsv = ko.computed(function() {
return self.students().map(function(s) { return s.txt(); }).join(", ");
});
self.childToBeEnrolled = ko.observable(null);
}
function Child(id, txt) {
var self = this;
self.id = ko.observable(id);
self.txt = ko.observable(txt);
self.classToBeEnrolledIn = ko.observable(null);
}
var english = new Class(1, "English 1");
var math1 = new Class(2, "Mathematics 1");
var math2 = new Class(2, "Mathematics 2");
var john = new Child(1, "John Doe");
var mary = new Child(1, "Mary Roe");
var rick = new Child(1, "Rick Roll");
var marc = new Child(1, "Marcus Aurelius");
var school = new School([english, math1, math2]);
ko.applyBindings(school);
// Method 1:
school.enroll(john, english);
school.enroll(john, math2);
school.enroll(marc, english);
school.enroll(mary, math2);
school.enroll(mary, english);
school.enroll(rick, english);
school.enroll(rick, math1);
td { background-color: #eee; padding: 2px 10px; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.0/knockout-min.js"></script>
<h3>Classes:</h3>
<table>
<tbody data-bind="foreach: classes">
<tr>
<td><span data-bind="text: txt"></span></td>
<td><span data-bind="text: studentsCsv"></span></td>
<td>
Add student
<select data-bind="options: $root.students, value: childToBeEnrolled, optionsText: 'txt', optionsCaption: 'Choose...'"></select>
<button data-bind="click: $root.enrollNewChild">enroll now</button>
</td>
</tr>
</tbody>
</table>
<h3>School Students</h3>
<table>
<tbody data-bind="foreach: students">
<tr>
<td><span data-bind="text: txt"></span></td>
<td>
Enroll in:
<select data-bind="options: $root.classes, optionsText: 'txt', value: classToBeEnrolledIn, optionsCaption: 'Choose...'"></select>
<button data-bind="click: $root.enrollInClass">enroll now</button>
</td>
</tr>
</tbody>
</table>
It does not answer your question directly ("display a filtered list of students based on the class id property") because I think that's an XY-problem, and you're better off trying to find a solution like the above where you have proper references instead of having to use id and some kind of lookup mechanism.
Yes I can see how it could be considered a bit of an XY problem. You both made look at it differently which was a great help.
The way I originally would have liked wasn't looking feasible. My compromise was to add a computed to the root view model and display the list this way.
function School()
{
var self = this;
self.ClassVMs = ko.observableArray([]).indexed('Number');
self.ChildVMs = ko.observableArray([]).indexed('Number');
self.DisplayClassId = ko.observable(1);
self.Display = function(x)
{
console.log(x);
self.DisplayClassId(x);
}
}
var viewModel = new School();
viewModel.filteredItems = ko.computed(function () {
var filter = viewModel.DisplayClassId();
if (!filter) {
return viewModel.ChildVMs();
} else {
var filtered = ko.utils.arrayFilter(viewModel.ChildVMs(), function (item) {
return (item.ClassId() === filter);
});
return filtered;
}
})
Fiddle for reference
I have a simple webpage with a large list of products (20,000+). When you can click on a product, it will load (via AJAX) a list of colors and display them inline. Html...
<div data-bind="foreach: products">
<span data-bind="click: $root.loadColors($data), text: $name"></span>
<ul data-bind="foreach: colors">
<li data-bind="text:$data" />
</ul
</div>
Shop view model:
function shopViewModel()
{
var self = this;
self.products = ko.observableArray([]);
self.loadColors = function(product)
{
var data = GetColorsByAjax();
product.colors(data);
}
}
Product view Model:
function productModel(data)
{
var self = this;
self.name = data.name;
self.colors = ko.observableArray([]);
}
When I have 20,000+ products, it uses a lot of memory. Each product has a colors array, which is always empty/null, until the user clicks on it, but it still uses a lot of memory.
Ideally, I'd like to remove the colors observableArray and somehow create it dynamically when user clicks on the product. Or separate it into a new viewModel.
I want to eliminate the empty observableArrays to minimise memory, but can't figure out how it do it.
I would use one of Knockout's control-flow bindings (if, with) to only bind the colors:foreach when there is actually a colors property on the productModel().
HTML:
<div data-bind="foreach: products">
<span data-bind="click: $root.loadColors($data), text: $name"></span>
<div data-bind="if: hasColors">
<ul data-bind="foreach: colors">
<li data-bind="text:$data" />
</ul>
</div>
</div>
Product View Model:
function productModel(data)
{
var self = this;
self.name = data.name;
self.hasColors = ko.observable(false);
self.colors = null;
}
Shop View Model
function shopViewModel()
{
var self = this;
self.products = ko.observableArray([]);
self.loadColors = function(product)
{
var data = GetColorsByAjax();
if(product.colors == null) {
product.colors = ko.observableArray(data);
product.hasColors(true);
} else {
product.colors(data);
}
}
}
You don't have to store an empty observable array: you can default to undefined and Knockout will treat it as an empty array in a foreach binding.
Here's a demonstration: http://jsfiddle.net/zm62T/
How do I used Knockout's "hasfocus" binding in Click-to-Edit (Example 2) on a page that has multiple field:value pairs? I have a page for View Customer Details, and I want to have this capability to edit upon double click.
You need to create an array of PersonViewModels and foreach loop them in the view. To reuse the example on the knockout page the code could look like this:
(function () {
function PersonViewModel(name) {
// Data
this.name = ko.observable(name);
this.editing = ko.observable(false);
// Behaviors
this.edit = function() { this.editing(true) }
}
function ViewModel(personModels) {
this.persons = ko.observableArray(personModels);
}
var personModels = [
new PersonViewModel('Bert'),
new PersonViewModel('James'),
new PersonViewModel('Eddy')
];
ko.applyBindings(new ViewModel(personModels));
})();
And the view:
<div data-bind="foreach: persons">
<p>
Name:
<b data-bind="visible: !editing(), text: name, click: edit"> </b>
<input data-bind="visible: editing, value: name, hasfocus: editing" />
</p>
<p><em>Click the name to edit it; click elsewhere to apply changes.</em></p>
</div>
Here's a jsfiddle demo: http://jsfiddle.net/danne567/gTHpu/
I'm having a nested array which represents a navigation (see the jsFiddle below). I want to render this navigation with knockoutJS but have no clue how. I already went through the official documentation, but they only cover a simple list/collection.
http://jsfiddle.net/a4swJ/
You need to use the template binding.
Update: I removed the containerless foreach and used to foreach option of the template binding instead. Working example below also updated
HTML:
<script type="text/html" id="node-template">
<li>
<a data-bind="text: Title, attr:{href: Target}"></a>
<ul data-bind="template: { name: 'node-template', foreach: Children }"></ul>
</li>
</script>
<ul data-bind="template: { name: 'node-template', foreach: Nodes }"></ul>
JS:
function NavigationNode(target, title)
{
var self = this;
self.Target = target || "[No Target]";
self.Title = title || "[No Title]";
self.Children = ko.observableArray([]);
};
function NavigationViewModel()
{
var self = this;
self.Nodes = ko.observableArray([]);
var node1 = new NavigationNode("/parent", "Parent");
var node2 = new NavigationNode("/parent/sub1", "Sub 1");
var node3 = new NavigationNode("/parent/sub1/sub2", "Sub 2");
node2.Children().push(node3);
node1.Children().push(node2);
self.Nodes.push(node1);
ko.applyBindings(this);
};
new NavigationViewModel();
Here's a jsFiddle.