I am using knockout in my project. I have multiple viewmodel, each viewmodel have its own save function implemented in it. Now whenever user clicks on save button the viewmodel data post to the server, i want to block the save button until the response came back from server.
Currently i am handling this by creating an extra observable property saving in each viewmodel. So when user click over the save button i am setting saving observable to true and in callback i am setting it to false. And i have bind this saving property with the button using knockout disable binding.
But i feel that this approach is not good and it contains the following big drawbacks:
For this i have to add an extra property in each viewmodel.
I have to add multiple line of code like setting it to true and again set it to false.
The approach is not centralize, the code for this approach is scattered.
So i want to know is there any other better way to handle this, a plugin or some standard way ??
Edit
Just to clarify, my question has nothing to do with asp.net postback, the question is how i can handle efficiently the ajax, like block the save button, displaying the response message etc
??
This is generally what makes a viewmodel a viewmodel. In a pattern like MVC, your controller shouldn't really have any idea what your view looks like, what controls it has, or what it's state is, and your model only contains data for the view to model. In an MVVM pattern, as knockout is, your viewModel actually does have knowledge of the current states of controls on the view. This isn't to say your viewmodel should directly update the view, but it usually will contain properties that are bound to states of the view. Things like SaveButtonEnabled or IsSavingData or even things like StatusLabelColor are accepted in a viewmodel.
Perhaps use $.ajaxSetup(). You call this in your document ready function.
$.ajaxSetup({
beforeSend: function(jqXHR)
{
//this will be called before every
//ajax call in your program
//so perhaps, increment an observable viewmodel variable
//representing the number of outstanding requests
//if this variable is > 0 then disable
//your button
},
complete: function(jqXHR)
{
//this will be called after every
//call returns
//decrement your variable here
//if variable is zero, then enable button
}
});
I'd recommend you take a look at http://durandaljs.com/, a framework using Knockout and has some great data patterns, even if you don't use it directly.
Related
I've tried to prepare data from an OData source to show it in a bar graph in my fiori app. For this, I setup the OData model in the manifest.json. A test with a list, simply using
items="{path : 'modelname>/dataset'}
works fine and shows the content.
To prepare data for a diagram (VizFrame), I used the onInit() function in the controller of the view (mvc:XMLView). The data preparation is similar to the one discussed in question.
At first I obtain the ODataModel:
var oODataModel = this.getOwnerComponent().getModel("modelname");
Next I do the binding:
var oBindings = oODataModel.bindList("/dataset");
Unfortunately, the oBindings().getContexts() array is always empty, and also oBindings.getLength() is zero. As a consequence, the VizFrame shows only "No Data".
May it be that the data model is not fully loaded during the onInit() function, or do I misunderstand the way to access data?
Thanks in advance
Update
I temporary solved the problem by using the automatically created bind from the view displaying the data as list. I grep the "dataReceived" event from the binding getView().byId("myList").getBindings("items") and do my calculation there. The model for the diagram (since it is used in a different view) is created in the Component.js, and registered in the Core sap.ui.getCore().setModel("graphModel").
I think this solution is dirty, because the graph data depends on the list data from a different view, which causes problems, e.g. when you use a growing list (because the data in the binding gets updated and a different range is selected from the odata model).
Any suggestions, how I can get the odata model entries without depending on a different list?
The following image outlines the lifecycle of your UI5 application.
Important are the steps which are highlighted with a red circle. Basically, in your onInit you don't have full access to your model via this.getView().getModel().
That's probably why you tried using this.getOwnerComponent().getModel(). This gives you access to the model, but it's not bound to the view yet so you don't get any contexts.
Similarly metadataLoaded() returns a Promise that is fullfilled a little too early: Right after the metadata has been loaded, which might be before any view binding has been done.
What I usually do is
use onBeforeRendering
This is the lifecycle hook that gets called right after onInit. The view and its models exist, but they are not yet shown to the user. Good possibility to do stuff with your model.
use onRouteMatched
This is not really a lifecycle hook but an event handler which can be bound to the router object of your app. Since you define the event handler in your onInit it will be called later (but not too late) and you can then do your desired stuff. This obviously works only if you've set up routing.
You'll have to wait until the models metadata has been loaded. Try this:
onInit: function() {
var oBindings;
var oODataModel = this.getComponent().getModel("modelname");
oODataModel.metadataLoaded().then(function() {
oBindings = oODataModel.bindList("/dataset");
}.bind(this));
},
May it be that the data model is not fully loaded during the onInit()
function, or do I misunderstand the way to access data?
You could test if your model is fully loaded by console log it before you do the list binding
console.log(oODataModel);
var oBindings = oODataModel.bindList("/dataset");
If your model contains no data, then that's the problem.
My basic misunderstanding was to force the use of the bindings. This seems to work only with UI elements, which organize the data handling. I switched to
oODataModel.read("/dataset", {success: function(oEvent) {
// do all my calculations on the oEvent.results array
// write result into graphModel
}
});
This whole calculation is in a function attached to the requestSent event of the graphModel, which is set as model for the VizFrame in the onBeforeRendering part of the view/controller.
Just wondering how people deal stopping multiple external server calls? I'm doing everything in the .complete of the fetch because otherwise when I try to call anything the fetch hasn't completed and nothing is populated in the collection.
I'm new to backbone so I'm probably missing a trick.. but is there a way to do a fetch and store that information somewhere so that you never have to fetch again, you just work off the collection as a variable? All of my information comes from an external site, so I don't want to be making lots of unnecessary external calls if I can. I'm not updating the server or anything, its all just read-only.
What do other people do for a similar set up? Am I missing something silly? Or am I set up badly for this? Here's what I have so far (work in progress)
Oh also: I'm doing the fetch in the router.. is that a bad idea?
http://jsfiddle.net/leapin_leprechaun/b8y6L0rf/
.complete(
//after the fetch has been completed
function(){
//create the initial buttons
//pull the unique leagues out
var uniqueLeagues = _.uniq(matches.pluck("league"));
//pull the unique leagues out
var uniqueDates = _.uniq(matches.pluck("matchDate"));
//pass to info to the relative functions to create buttons
getLeagues(uniqueLeagues);
getMatchDates(uniqueDates);
homeBtn();
fetched = true;
}
); //end complete
Thanks for your time!
This is an often recurring question but the answer is rather simple.
Perhaps I'll make some drawings today, if it helps.
I never took the time to learn UML properly, so forgive me for that.
1. The problem
What you currently have is this:
The problem however is that this isn't very dynamic.
If these 3 functions at the right would require to be executed from different ajax callback functions, they need to be added to any of these callbacks.
Imagine that you want to change the name of any of these 3 functions, it means that your code would break instantly, and you would need to update each of these callbacks.
Your question indicates that you feel that you want to avoid every function to perform the async call separately, which is indeed the case because this creates unnecessary overhead.
2. Event aggregation
The solutions is to implement an event driven approach, which works like this:
This pattern is also called pub/sub (or observer pattern) because there are objects that publish events (in this case on the left) and objects that subscribe (on the right).
With this pattern, you don't need to call every function explicitly after the ajax callback is finished; rather, the objects subscribe to certain events, and execute methods when the event gets triggered. This way you are always certain that the methods will be executed.
Note that when triggering an event, parameters can be passed as well, which allows you to access the collection from the subscribing objects.
3. Backbone implementation
Backbone promotes an event driven approach.
Setting up an event aggregator is simple and can be done as follows:
window.APP = {};
APP.vent = _.extend({}, Backbone.Events);
From the ajax callback, you just trigger an event (you give it any name you want, but by convention, a semi colon is used as a separator):
APP.vent.trigger("some:event", collection);
The three receiving objects subscribe to the event as follows:
APP.vent.on("some:event", function(collection){
console.log(collection.toJSON());
});
And that's basically all.
One thing to take into account is to make sure that when you subscribe to events using "on", you also need to un-subscribe by calling "off", if you no longer need the object.
How to handle that is all up to you in Backbone.js but here is one of options you can take
Creating a View which has body as its el and handle everything.(I usually use Coffee so This might has some syntax errors)
$( document ).ready(function() {
mainView = new MainView({el: "body"});
});
MainView = Backbone.View.extend({
initialize : function(){
this.prepareCollection();
},
prepareCollection : function(collection){
_checker = function(){
if (collection.length === _done) {
this.render();
}
};
_.bind(_checker,this);
collection.each(function(item){
item.fetch(
success : function(){
//you can also initialize router here.
_checker();
}
);
});
},
rener : function(){
//make instance of View whichever you want and you can use colleciton just like variable
}
})
I've inherited a project which uses Knockout.JS to render a listing of posts. The client has asked that this listing be paginated and I'm wondering if this is possible and appropriate using Knockout.JS. I could easily achieve this in pure JavaScript but I'd like to use Knockout (if appropriate) for consistency.
From what I can tell, the page uses a Native Template in the HTML of the page. There is a ViweModel which stores the posts in a ko.ObservableArray() and a post model.
The data is loaded via a jQuery ajax call where the returned JSON is mapped to post model objects and then passed into the ObservableArray which takes care of the databinding.
Is it possible to amend the ViewModel to bind pagination links (including "previous" and "next" links when required) or would I be better off writing this in plain JS?
It should be easy enough to build a computed observable in knockout that shows a "window" of the full pagelist. For example add to the view model:
this.pageIndex = ko.observable(1);
this.pagedList = ko.computed(function() {
var startIndex = (this.pageIndex()-1) * PAGE_SIZE;
var endIndex = startIndex + PAGE_SIZE;
return this.fullList().slice(startIndex, endIndex);
}, this);
Then bind the "foreach" binding showing the record to pagedList instead of the full list, and in the forward and back links, simply change the value of pageIndex. Starting from there, you should be able to make it more robust/provide more functionality.
Also, this assumes you preload all data to the client anyway. It's also possible to make JSON calls on the previous and next link and update the model with the returned items. The "next" function (to be added to the view model prototype), could look like this:
ViewModel.prototype.next = function() {
var self = this;
this.pageIndex(this.pageIndex()+1);
$.ajax("dataurl/page/" + this.pageIndex(), {
success: function(data) {
self.dataList(data);
}
});
}
(using jQuery syntax for the ajax call for brevity, but any method is fine)
Writing features in KO always tend to generate less code and cleaner code than doing the same in "plain JS", jQuery or similar. So go for it!
I implemented a combobox with paging like this
https://github.com/AndersMalmgren/Knockout.Combobox/blob/master/src/knockout.combobox.js#L229
In my blog post, I have explained in very detail how to do it. you can find it (here. http://contractnamespace.blogspot.com/2014/02/pagination-with-knockout-jquery.html). It's very easy to implement and you can do it with a simple JQuery plugin.
Basically, I have used normal knockout data binding with AJAX and after data has been retrieved from the server, I call the plugin. You can find the plugin here. its called Simple Pagination.
I have a list of images each with a 'Like' button. When the 'Like' button is clicked, an AJAX request (containing the item_id and user_id) will be sent to the serverside to record the Like (by adding a new row in the table likes with values for item_id and user_id).
The model Photo is used for the images displayed on the page. If I understand correctly, this.model.save() is used if I want to update/add a new Photo, so it is not suitable for recording 'Likes'. Therefore, I have to use something like $.get() or $.post(). Is this the conventional way?
Or do I create a new model called Like as shown below, which seems to make it messier to have a View and template just for a Like button.
Like = Backbone.Model.extend({
url: 'likes'
});
LikeView = Backbone.View.extend({
template: _.template( $('#tpl-like').html() ),
events: {
'click .btn_like': 'like'
},
like: function() {
this.model.save({
user_id: 1234,
post_id: 10000
})
}
});
In similar cases to this I've used the $.get method rather than create a new model, obviously this will depend on your application, but here are my reasons.
This case appears to have the following characteristics:
Like is a relationship between a person and a photo,
you seem to have a server side resource that accepts the photo and user ids to create this relationship already,
you probably have no other information attached to that relationship, and
you probably don't have significant view logic to go with the like itself
This is better handled by adding another attribute to your Photo object, that contains the number of likes. Then use $.get to create the like, and a 200 response will simply update the photo object to up it's count (and hence the view). Then the server side just needs to include the like count as part of it when it returns.
I'm assuming here that once a like is made you won't be updating it. If you do need to update or delete it, I might still keep using the $.get. You can add a likes array to your photo object where each element is the id of the like resource. The view will display the length of the array as the count, and if you need to delete the like, you have access to the id and you can use $.post. Just make sure you don't use .push to add values to your array since that'll bypass backbone's set method and you won't get your event callbacks. You need to clone the array, then push, and then set it when you make changes.
I have an application in ASP.MVC. The requirement is that I select a person from a list of people and click 'Info' and it should load the details of the person in that page. I have the Info controller and everything works fine if I go to the Info page from a different controller. In the page I am trying to make it work with JavaScript and it doesn't seem to take me to the desired page but to a different controller.
I have a ToDoList controller and in the .cshtml I have this code on click of the Info link.
function DoInfo#(i.ToString())() {
$("#sessionid").val("#Model.cSessionId[i]");
alert("hey");
$("#PageController").val(66);
$("#formID").submit();
}
I go to the ToDoList controller to do the redirection like this
if (viewModel.PageController == 66)
{
pass = new PassingData();
pass.personid = TSSessionService.ReadPersonId(viewModel.SessionId);
TempData["pass"] = pass;
return RedirectToAction("Index", "Info");
}
It never goes there and instead goes to a different controller. I cannot seem to find how they are linked and why is it not going back to controller where the Info link button is i.e. back to the ToDoList controller.
Let me know if it is not clear and I will try to explain again and I will give any other details.
I guess I'm confused as to why you are doing this as a combination of form and JavaScript. Are there other properties that you need to pass along that you are not posting above? Why do you need to use JavaScript to do this if you are just returning a new view?
You indicate in your post that when a person is selected from a list you need to go to a controller and display a view. This seems fairly straightforward, and I would like to suggest simplifying the problem.
Start with this: change your link to not use a form or JavaScript. Just make it a link. If it is text, you can use #Html.ActionLink() and even pass in the parameters you need.
If you're not displaying text, just use #Url.ActionLink() in your href property of the anchor you're wrapping your element with. Both of these allow you to leverage routing to ensure the correct path is being constructed.
If the controller that you are trying to get to has access to whatever TSSessionService is, then you don't need to pass through the TempData["pass"] you are trying to push through, so it makes it cleaner in that way as well.
If you do need to submit a more complicated value set, I would recommend coming up with a generic .click() event handler in jQuery that can respond to any of the clicks, bound by a common class name. You can use a data-val attribute in your link and read from $(this).attr('data-val') in your handler to store/fetch other important info. This allows you to more easily build up an object to POST to a controller.
Hope this helps some, but if I'm missing a critical point then please update the question above.