I have what is likely a simple Knockout question but I'm a complete beginner with it. I was tossed this page of code that someone else has worked on but never finished.
When this page first loads, the data is retrieved and the main grid loads properly. The problem comes in when I attempt to auto-select the first record in the results so that a detail list gets filled out below the grid.
When that happens, I receive the following message.
Uncaught TypeError: Unable to process binding "text: function (){return selected.RequestLog.Timestamp }" , Message: Cannot read property 'Timestamp' of undefined
Here is the code snippets with which I'm working. The data coming back is from Entity Framework.
var siteLogModel = function () {
var self = this;
self.errorList = ko.observableArray([]);
self.selected = ko.observable();
self.updateErrorList = function (page) {
jQuery.ajax({
type: "POST",
url: "/Admin/ErrorPage",
data: { pageNum: page },
success: function (result) {
self.errorList(result);
self.selected(result[0]);
// Since we have success, add the click handler so we can get the details about a row by id.
//addRowHandlers();
},
error: function (result) {
jQuery("#status").text = result;
}
});
};
};
This is the actual binding that tries to happen after the data is loaded. RequestLog does not seem to exist at binding time, even though it does seem to be ok if I set a breakpoint in the above function on the line self.selected(result[0]).
I think this is a scope problem but I can't for the life of me think of how best to fix it. Any help would be appreciated.
<div class="param">
<span>Time</span>
<label data-bind="text: selected.RequestLog.Timestamp"></label>
</div>
UPDATE: Here is the document ready portion.
jQuery(document).ready(function () {
var vm = new siteLogModel();
vm.updateErrorList(0);
ko.applyBindings(vm);
});
Your selected observable does not have a .RequestLog property at the time ko is evaluating the binding expression. That error is coming from javascript, not ko (though ko wraps the exception in the error message you see). When running, selected.RequestLog === undefined is true, and you can't invoke anything on undefined. It's like a null reference exception.
It makes sense if you are calling applyBindings before the ajax call finishes.
One way to fix this by doing a computed instead:
<div class="param">
<span>Time</span>
<label data-bind="text: selectedRequestLogTimestamp"></label>
</div>
self.selectedRequestLogTimestamp = ko.computed(function() {
var selected = self.selected();
return selected && selected.RequestLog
? selected.RequestLog.TimeStamp
: 'Still waiting on data...';
});
With the above, nothing is ever being invoked on an undefined variable. Your label will display "Still waiting on data" until the ajax call finishes, then it will populate with the timestamp as soon as you invoke self.selected(result[0]).
Another way to solve it is by keeping your binding the same, but by giving the selected observable an initial value. You can leave all of your html as-is, and just to this:
self.selected = ko.observable({
RequestLog: {
TimeStamp: 'Still waiting on data'
}
});
... and you will end up with the same result.
Why?
Any time you initialize an observable by doing something like self.prop = ko.observable(), the actual value of the observable is undefined. Try it out:
self.prop1 = ko.observable();
var prop1Value = self.prop1();
if (typeof prop1Value === 'undefined') alert('It is undefined');
else alert('this alert will not pop up unless you initialize the observable');
So to summarize what is happening:
You initialize your selected observable with a value equal to undefined in your viewmodel.
You call ko.applyBindings against the viewmodel.
ko parses the data-bind attributes, and tries to bind.
ko gets to the text: selected.RequestLog.Timestamp binding.
ko invokes selected(), which returns undefined.
ko tries to invoke .RequestLog on undefined.
ko throws an error, because undefined does not have a .RequestLog property.
All of this happens before your ajax call returns.
Reply to comment #1
Yes, you can call applyBindings after your ajax success event. However, that's typically not always what you should do. If you want to, here's one example of how it could be done:
self.updateErrorList = function (page) {
self.updateErrorPromise = jQuery.ajax({
type: "POST",
url: "/Admin/ErrorPage",
data: { pageNum: page },
success: function (result) {
self.errorList(result);
self.selected(result[0]);
},
error: function (result) {
jQuery("#status").text = result;
}
});
};
jQuery(document).ready(function () {
var vm = new siteLogModel();
vm.updateErrorList(0);
vm.updateErrorPromise.done(function() {
ko.applyBindings(vm);
});
});
Yet another way would be to go ahead and eager-bind (applyBindings before the ajax call finishes), but wrap your markup in an if binding like so:
<div class="param" data-bind="if: selected">
<span>Time</span>
<label data-bind="text: selected.RequestLog.Timestamp"></label>
</div>
Related
I'm having some problems with users clicking buttons multiple times and I want to suppress/ignore clicks while the first Ajax request does its thing. For example if a user wants add items to their shopping cart, they click the add button. If they click the add button multiple times, it throws a PK violation because its trying to insert duplicate items into a cart.
So there are some possible solutions mentioned here: Prevent a double click on a button with knockout.js
and here: How to prevent a double-click using jQuery?
However, I'm wondering if the approach below is another possible solution. Currently I use a transparent "Saving" div that covers the entire screen to try to prevent click throughs, but still some people manage to get a double click in. I'm assuming because they can click faster than the div can render. To combat this, I'm trying to put a lock on the Ajax call using a global variable.
The Button
<span style="SomeStyles">Add</span>
Knockout executes this script on button click
vmProductsIndex.AddItemToCart = function (item) {
if (!app.ajaxService.inCriticalSection()) {
app.ajaxService.criticalSection(true);
app.ajaxService.ajaxPostJson("#Url.Action("AddItemToCart", "Products")",
ko.mapping.toJSON(item),
function (result) {
ko.mapping.fromJS(result, vmProductsIndex.CartSummary);
item.InCart(true);
item.QuantityOriginal(item.Quantity());
},
function (result) {
$("#error-modal").modal();
},
vmProductsIndex.ModalErrors);
app.ajaxService.criticalSection(false);
}
}
That calls this script
(function (app) {
"use strict";
var criticalSectionInd = false;
app.ajaxService = (function () {
var ajaxPostJson = function (method, jsonIn, callback, errorCallback, errorArray) {
//Add the item to the cart
}
};
var inCriticalSection = function () {
if (criticalSectionInd)
return true;
else
return false;
};
var criticalSection = function (flag) {
criticalSectionInd = flag;
};
// returns the app.ajaxService object with these functions defined
return {
ajaxPostJson: ajaxPostJson,
ajaxGetJson: ajaxGetJson,
setAntiForgeryTokenData: setAntiForgeryTokenData,
inCriticalSection: inCriticalSection,
criticalSection: criticalSection
};
})();
}(app));
The problem is still I can spam click the button and get the primary key violation. I don't know if this approach is just flawed and Knockout isn't quick enough to update the button's visible binding before the first Ajax call finishes or if every time they click the button a new instance of the criticalSectionInd is created and not truely acting as a global variable.
If I'm going about it wrong I'll use the approaches mentioned in the other posts, its just this approach seems simpler to implement without having to refactor all of my buttons to use the jQuery One() feature.
You should set app.ajaxService.criticalSection(false); in the callback methods.
right now you are executing this line of code at the end of your if clause and not inside of the success or error callback, so it gets executed before your ajax call is finished.
vmProductsIndex.AddItemToCart = function (item) {
if (!app.ajaxService.inCriticalSection()) {
app.ajaxService.criticalSection(true);
app.ajaxService.ajaxPostJson("#Url.Action("AddItemToCart", "Products")",
ko.mapping.toJSON(item),
function (result) {
ko.mapping.fromJS(result, vmProductsIndex.CartSummary);
item.InCart(true);
item.QuantityOriginal(item.Quantity());
app.ajaxService.criticalSection(false);
},
function (result) {
$("#error-modal").modal();
app.ajaxService.criticalSection(false);
},
vmProductsIndex.ModalErrors);
}
}
you could use the "disable" binding from knockout to prevent the click binding of the anchor tag to be fired.
here is a little snippet for that. just set a flag to true when your action starts and set it to false again when execution is finished. in the meantime, the disable binding prevents the user from executing the click function.
function viewModel(){
var self = this;
self.disableAnchor = ko.observable(false);
self.randomList = ko.observableArray();
self.loading = ko.observable(false);
self.doWork = function(){
if(self.loading()) return;
self.loading(true);
setTimeout(function(){
self.randomList.push("Item " + (self.randomList().length + 1));
self.loading(false);
}, 1000);
}
}
ko.applyBindings(new viewModel());
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.0.0/knockout-min.js"></script>
Click me
<br />
<div data-bind="visible: loading">...Loading...</div>
<br />
<div data-bind="foreach: randomList">
<div data-bind="text: $data"></div>
</div>
I have this code Ext.get('book').setValue('1');
Note: Loads the page and book value is set to 1. Not after page load
and book value change to 1.
It sets the book to value 1. But it does not trigger a change event. Is there a way to trigger the change event after page loads?
Edit:
In html script,
<script..>
$(document).ready(function () {
$("book").on("blur", function() {
//calls other function
}); // not called as blur is not invoked
});
</script>
<input id="book" type="book" value="" /><br />
In extjs,
var panel = Ext.create('Ext.grid.Panel', {
id: 'panel',
columns: [
var bookid = "new book";
Ext.Ajax.request({
params: { bookid: bookid},
function: function (response) {
Ext.get('book').setValue(bookid);
// after setValue, book will receive a change event(e.g .blur in html) and changes other functions
}
});
]
});
Your ajax request seems to be malformed, the function: function statement would be the place where you put normally success: function like in the following statement:
Ext.Ajax.request({
url: 'insert-your-http-endpoint-here',
params: {
bookid: bookid
},
success: function(response){
debugger; // -> setting this statement will show that you enter the success statement
Ext.get('book').setValue(bookid);
},
failure: function(response, opts) {
// something went wrong with your request
console.log('server-side failure with status code ' + response.status);
}
});
more info about how to use ExtJS or the specific function, you could find in the documentation (check if you have the correct version, ofcourse) which can be found here
From the above code, you don't need the debugger statement, but it could help if you want to check if you actually get into this code block or not, and what happens when you try to set the value.
Also, don't forget to check your console output when something is not working, maybe there was a problem that would be clearly indicated in the console log
I have created a table and I am using http to load the data in the tables. So, in every click, my table data is changing, but I don't see the updated data in the table.
I had created a sample Plunker for the reference. In my project, WHen I click on Reload New Data, the data in table get's changed, but after 2-3 click it doesn't change. DId anyone know, how to fix it..
It is a problem with the ngTable directive. It updates only when data.length changes. Take a look at this plunk. I set $scope['tableParams1'] to null and inside the $timeout I set the new data. This forces angularJs to do a new cycle. So in the first cycle the ngTable sees the data.length changed to 0 and in the new cycle the ngTable sees the data.length changed again. If you don't use the $timeout, the ngTable will see that the data.length remains the same as before and won't do nothing.
With some trial and error I found a seemingly better solution to the issue than indicated in the plunkrs. For clarity, I am using $resource in a service to fetch my data. When I add a record via a modal, at first it wouldn't upload the ng-table after closing the modal. I figured out a way that works for me:
// Get data from factory
var data = dataFactory.query();
//Use promise to load data to table, note the replacing of the second tableParams
//object parameter with a function
data.$promise.then(function (data){
$scope.tableParams = new ngTableParams({
page: 1, // show first page
count: 10,
sorting: {
name: 'asc'
},
filter: {
name: undefined
}
}, resetTableParams()
);
});
//The function that replaces the tableParams param
var resetTableParams = function(){
return {
total: data.length,
getData: function($defer, params) {
var filteredData = params.filter() ? $filter('filter')(data, params.filter()) : data;
var orderedData = params.sorting() ? $filter('orderBy')(data, params.orderBy()) : filteredData;
params.total(orderedData.length);
$defer.resolve($scope.data = orderedData.slice((params.page() -1) * params.count(), params.page() * params.count()));
}
}
}
//A method to update the table that can be called when closing a modal
var updateTable = function(){
data = dataFactory.query();
data.$promise.then(function (data){
$scope.tableParams.reload();
});
}
// Add table row to table in modal and call updateTable() on closing modal
$scope.addRow = function(){
var modalInstance = $modal.open({
templateUrl: 'resources/partials/newrecord.html',
controller: NewRecordModalCtrl
})
modalInstance.result.then(function(){
updateTable();
});
}
Unfortunately, I can't give a clear explanation as to why this works and other methods don't. For instance, if you would not use the resetTableparams() function but leave it hardcoded, the table does not update. Somehow, Angular's digest cycle likes this better :) If somebody has a good explanation, please share!
You can directly use the provided method $scope.tableParams.reload();
I'm not sure about the exact cause of the incorrect incrementing, but the problem here may be more due to the approach. You should attach the count to the scope via $scope.count, and then use the ng-click directive to increment it: <button type="button" ng-click="count++;".
It would also make it easier for you/others to read and debug if you externalized the $scope.tableParams and the data from $scope.table1 conditional thing:
$scope.count = 0;
var dataCollections = [
[//.. first collection],
[//.. second collection],
[//.. third collection],
[//.. fourth collection]
];
$scope.data = dataCollections[0];
$scope.$watch('count', function () {
$scope.data = $scope.count < 4 ? dataCollections[$scope.count] : dataCollections[3];
});
I'm also not sure what you've got going on there with the $compile inside of the controller. It might make your task easier if you investigated some stuff about writing Angular controllers before delving into using a third-party module.
I was working on ng-tables with dynamic data as well (adding/removing),
I was using an ajax call to make changes to the database, and the success: function() {} property make changes to the tableParams
but changes wouldn't show on the page unless i refreshed it, with a few console.log()'s, I found out that the success: function() {} actually never executes
but there's another function that always executes, complete: function() {}
I know it's logically wrong to put the code that's supposed to work only after a successful call into complete: function() {} but if my success: function isn't working, this fix isn't that bad, especially knowing that the change is always successfully made to the database
it's strange because the success call works on other pages of the website, but it doesn't on some others.
EDIT:
well, this fix still doesn't solve the problem when the length of the data doesn't change "editing the text in the data" as mentioned above,, frustrating...
$.ajax({
type: "POST",
url: /*some url*/,
data: JSON.stringify({ /*some variable*/ }
}),
contentType: "application/json; charset=utf-8",
dataType: "Json",
success: function () { // would never execute even if it's a successful call
console.log("success");
},
error: function() { // optional, personally didn't try it
console.log("error");
}
complete: function () { //always executes regardless of the result
console.log("complete");
}
});
To solve the issue, make sure you have set the ng-controller="yourController" only once in your page.
Code below will not update data:
<div ng-controller="yourController">
<table ng-table = "tableParams" ng-controller = "yourController">
</table>
</div>
Solve the issue by removing extra ng-controller in your html page:
<div ng-controller="yourController">
<table ng-table = "tableParams">
</table>
</div>
I have a sortable accordion loaded with a foreach-template loop over a ko.observableArray() named "Tasks".
In the accordion I render the TaskId, the TaskName, and a task Description - all ko.observable().
TaskName and Description is rendered in input/textarea elements.
Whenever TaskName or Description is changed, an item is de-selected, or another item is clicked on, I want to call a function saveEdit(item) to send the updated TaskName and Description to the database via an ajax request.
I need to match the TaskId with the Tasks-array to fetch the actual key/value-pair to send to the saveEdit().
This is the HTML:
<div id="accordion" data-bind="jqAccordion:{},template: {name: 'task-template',foreach: Tasks,afteradd: function(elem){$(elem).trigger('valueChanged');}}"></div>
<script type="text/html" id="task-template">
<div data-bind="attr: {'id': 'Task' + TaskId}" class="group">
<h3><b><span data-bind="text: TaskId"></span>: <input name="TaskName" data-bind="value: TaskName /></b></h3>
<p>
<label for="Description" >Description:</label><textarea name="Description" data-bind="value: Description"></textarea>
</p>
</div>
</script>
This is the binding:
ko.bindingHandlers.jqAccordion = {
init: function(element, valueAccessor) {
var options = valueAccessor();
$(element).accordion(options);
$(element).bind("valueChanged",function(){
ko.bindingHandlers.jqAccordion.update(element,valueAccessor);
});
},
update: function(element,valueAccessor) {
var options = valueAccessor();
$(element).accordion('destroy').accordion(
{
// options put here....
header: "> div > h3"
, collapsible: true
, active: false
, heightStyle: "content"
})
.sortable({
axis: "y",
handle: "h3",
stop: function (event, ui) {
var items = [];
ui.item.siblings().andSelf().each(function () {
//compare data('index') and the real index
if ($(this).data('index') != $(this).index()) {
items.push(this.id);
}
});
// IE doesn't register the blur when sorting
// so trigger focusout handlers to remove .ui-state-focus
ui.item.children("h3").triggerHandler("focusout");
if (items.length) $("#sekvens3").text(items.join(','));
ui.item.parent().trigger('stop');
}
})
.on('stop', function () {
$(this).siblings().andSelf().each(function (i) {
$(this).data('index', i);
});
})
.trigger('stop');
};
};
My first thought was to place the line
$root.SelectedTask( ui.options.active );
in an .on('click') event function where SelectedTask is a ko.observable defined in my viewModel. However, the .on('click') event seems to be called a lot and it's generating a lot of traffic. Also, I can´t quite figure out where to put the save(item) call that sends the selected "item" from Tasks via an ajax-function to the database.
Any help is highly appreciated. Thanks in advance! :)
Whenever TaskName or Description is changed, an item is de-selected, or another item is clicked on, I want to call a function saveEdit(item) to send the updated TaskName and Description to the database via an ajax request.
This sounds like the core of what you want to do. Let's start out with a Task model
function Task (data) {
var self = this;
data = data || {};
self.id = ko.observable(data.id);
self.name = ko.observable(data.name);
self.description = ko.observable(data.description);
}
And then we need our View Model:
function ViewModel () {
var self = this;
self.tasks = ko.observableArray();
self.selectedTask = ko.observable();
self.saveTask = function (task) {
$.ajax({ ... });// ajax call that sends the changed data to the server
};
var taskSubscription = function (newValue) {
self.saveTask(self.selectedTask());
};
var nameSubscription, descriptionSubscription;
self.selectedTask.subscribe(function (newlySelectedTask) {
if (newlySelectedTask instanceof Task) {
nameSubscription =
newlySelectedTask.name.subscribe(taskSubscription);
descriptionSubscription =
newlySelectedTask.description.subscribe(taskSubscription);
self.saveTask(newlySelectedTask);// But why?
}
});
self.selectedTask.subscribe(function (currentlySelectedTask) {
if (currentlySelectedTask instanceof Task) {
nameSubscription.dispose();
descriptionSubscription.dispose();
self.saveTask(currentlySelectedTask);// But why?
}
}, null, 'beforeChange');
}
So what's going on here? Most of this should be pretty self explanatory so I'm just going to focus on the subscriptions. We created a taskSubscription function so we're not constantly having it defined every time the self.selectedTask changes.
We have two subscriber functions. The first fires after the selectedTask's value has changed and the second fires before it changes. In both, we verify that the new value is an instance of a Task object. In the after change subscription, we set up two subscriptions on the name and description properties. Then I capture the return value from the subscription function into two private variables. These are used in the before change function to dispose of those subscriptions so that if those Tasks are ever updated when they're not currently selected, then we don't continue to fire off the saveTask function.
I've also added self.saveTask in each of the subscriptions to the selectedTask observable. I asked why in here because, why save it if we don't know if the value has changed or not? You may be making ajax requests needlessly here.
Also, as demonstrated by this code, you can set up these subscriptions to make ajax requests every time the value changes but that may end up making a LOT of requests. A better option might be to set up functionality in your Task model that can track whether or not it is 'dirty' or not. Meaning one or more of its values have changed that requires updating.
function Task (data) {
var self = this;
// Make a copy of the data object coming in and use this to save previous values
self._data = data = $.extend(true, { id: null, name: null, description: null }, data);
self.id = ko.observable(data.id);
self.name = ko.observable(data.name);
self.description = ko.observable(data.description);
for (var prop in data) {
if (ko.isSubscribable(self[prop])) {
self[prop].subscribe(function (oldValue) {
data[prop] = oldValue;
}, null, 'beforeChange');
}
}
}
Task.prototype.isDirty = function () {
var self = this;
for (var prop in self._data) {
if (ko.isSubscribable(self[prop])) {
if (self._data[prop] !== self[prop]())
return true;
}
}
return false;
};
And of course you need a way to save it, or make it not dirty
Task.prototype.save = function () {
var self = this;
for (var prop in self._data) {
if (ko.isSubscribable(self[prop])) {
self._data[prop] = self[prop]();
}
}
};
Using the same concept you can also create Task.prototype.revert that does the opposite of what .save does. With all this in place, you could forego setting up the subscriptions on the individual name and description properties. I wanted to show that option to just demonstrate how one might want to use the .dispose method on a subscription. But now you can just subscribe to the selectedTask observable ('beforeChange') and see if the currently selected task that you're about to swap out isDirty. If it is, call the saveTask function, and when that completes, call the .save function on the Task so that it is no longer dirty.
This is probably the route I would go in implementing something like this. The beauty of it is, I haven't written a single line of code that has anything to do with the manipulating the View. You can set the selectedTask any way you see fit. What I would do is, bind the selectedTask observable to a click binding on the <h3> element inside of the accordion. That way, every time a user clicks on any of the accordions, it will potentially save the previously selected task (if any of the property values had changed).
Hopefully that addresses your scenario here of trying to save a Task when certain events are triggered.
I'm having issues with scope in Javascript. Take a look at this code, for example:
$(function() {
var items = "GLOBAL";
$('.add').click(function() {
$.post("main/get", { 'get' : 'all' },
function(data){
items = String(data.result);
items = items.split(' *** ');
alert(items);
}, "json");
alert(items);
return false;
});
$(".add").autocomplete({
source: items
});
});
I'm trying to get autocomplete working, and it almost is. The only problem is that I can't seem to change items outside of the inner-most function. The first alert gives me what I'm looking for, but the second just gives me "GLOBAL." The bottom autocomplete part has to be able to access it.
Any help is appreciated!
Thanks!
It is not just a scope issue. Since your request is very likely to happen asynchronously (unless configured otherwise) it won't work that way anyway. You have to initialize the autocomplete in the callback function which gets called once your AJAX request is complete:
$(function() {
$('.add').click(function() {
$.post("main/get", { 'get' : 'all' },
function(data){
var items = String(data.result);
items = items.split(' *** ');
$(".add").autocomplete({
source: items
});
}, "json");
});
});