I have an MVC Razor site and looking at adding about three AJAX forms on a page, inside each form will have a partial.
Is this good practice? Should the page be limited to one AJAX form per page?
Cheers
It is fine to have multiple Ajax forms on a page. That is why you have Single Page Application (SPA) frameworks. It is not so much a technical issue, rather a conceptual issue.
Does it make sense to have multiple forms on a single page?
If the answer is Yes then proceed. I would just think about that question long and hard before proceeding forward.
inside each form will have a partial.
Not sure what you meant by that.
You can have as many AJAX forms per page as your heart desires. If the forms all post to different resources (Or controllers) there's not real clean way around it. However, if they're posting to the same resource, you might want to re-think that controller's logic.
-Just one man's opinion.
Depends on your requirement. There is nothing which stops you from having multiple forms. The usage of form is generally for triggering non-idempotent requests to the server which potentially changes some state, however there are cases where multiple forms are used on single page like a page having a details submit functionality as well as an advanced search form which displays the results in a part of the page. Also there are things like Single page Interface.
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I used to utilize MVC 3 Razor engine to render pages. Sometimes I had to use AJAX calls to transfer Razor-rendered HTML and inserting it into the page using JQuery. As new project is starting, we do consider to utilize MVC 4 Single Page Application framework which is new to us. I took the first glance at it which left me with mixed feelings:
On the one hand it implies all your data are transferred by JSON and client does all the job to render them and encode some UI-related logic which is great for server and network performance. On the other hand the client (HTML+JavaScript) becomes much more heavy with a bunch of magic strings and hidden relations inside it which seems to be hard to maintain. We got used to VS intellisense, type-safed .NET server code to render pages which we have to exchange for client scripts and Knockout binding statements in case of SPA.
I wonder are any prons and cons of using SPA comparing to Razor, other that this obvious one I've mentioned here? Thanks
Razor is a server based technology where SPA (Single Page Application) is an architecture approach used on the client (web browser). Both can be used together.
From a high level, SPA moves the rendering and data retrieval to the client. The web server becomes a services tier sitting in front of the database. An MVC pattern works best when using SPA. Frameworks like Knockout.js and Backbone.js can be used for this. The net results is a rich responsive desktop like experience.
To achieve this you'll need to be a descent javascript programmer or be willing to learn javascript.
Yes it's moving business requirements from C# into javascript. In Visual Studio there is limited intelli-sense for javascript. To have confidence in your javascript you'll need to lean on unit testing. The up side is the rich user experience (think gmail or google maps).
I think it sounds like you are already fairly well apprised of most of the trade-offs here; you'll have reduced network load with SPA, and will shift a measure of the processing to the client. You will, however, increase the complexity of your code, and make it slightly harder to easily maintain the system (simply because of the increased complexity - not due to any architectural problems inherent in SPA).
Another thing to keep in mind is compatibility. The reason I mentioned a "false choice" in my comment to your question is that to keep the site usable for folks with Javascript disabled, you will still need to provide regular, whole-page views. This is also a good idea to do for the sake of SEO; a crawler will browse your site as a user with JS disabled, and can then index your site. The site should then handle such incoming URLs properly so that those with JS enabled will find themselves in your SPA looking at the same content (as opposed to being dumped in the "no JS" view unnecessarily).
There's something else I'll mention as a possibility that might help with the above, but it breaks the ideals of an SPA; that is, using Ajax-loaded partials in some places, rather than JSON data. For example, say you have a typical "Contact EMail" form on the site; you want that to load within the context of the SPA, but it's probably easier to do so by loading the partial via AJAX. (Though certainly, yes; you could do it with a JSON object describing the fields to display in the e-mail form).
There will also likely be content that is more "content" than "data", which you may still wish to load via partials and Ajax.
An SPA is definitely an interesting project, and I'm about to deploy one myself. I've used a mix of JSON and partials in it, but that may not be your own choice.
We have web applications elgifto.com, roadbrake.com in which we used AJAX at many places, especially to update major portions of a page. All the important functionality of elgifto.com was implemented using AJAX. Now we realize a few issues due to AJAX implementation.
All the content implemented using
AJAX is not available to the SEO
bots and it is hurting the page rank
of our site.
Users will not be able to bookmark
some of the pages as they are always
available through AJAX.
When we want to direct the user from
one page through an anchor link to
another page having AJAX, we find it
difficult.
So now we are thinking of removing AJAX for these pages and use it only for small functionality such as something similar to marking a question as favorite in SO. So before going ahead and removing, we want to know expert's opinion on this. Thanks.
The problem is not "AJAX" per se, but your implementation of it. Just as a for instance, you can fix the 'bookmark' problem like google maps does it: provide a generated link for each state of your webapp.
SEO can befixed by supplying various of these state-links to the crawlers, either organically trough links in your site, or by supplying a list (sitemap).
If you implement 2, you can fix 1 and 3 with those links.
In the end you must figure out if the effort is worth it, and if you are not overusing AJAX ofcourse, but the statements you've made are not set in stone at all.
I'm costantly developing ajax based websites, with no problems for SEO at all. You just have to use it in the best possible way.
For example, I have a website with normal links pointing to normal webpages (PHP pages), this for normal navigation if a user doesn't have JS enabled. But if a user has JS enabled, a script will change the links behavior, only fetching the content of the page needed.
This way you still have phisycal separated webpages with all their content, which will be indexed as normal.
I am working on a .Net MVC2 project where I am trying to modularize functionality as much as possible. One aspect of this would be to place a form in a partial views which is then called using RenderAction. This is so that the form's GET, POST, validation and redirection can be handled independently of the parent view.
I have read blogs and forums etc that suggest that this is not ideal behaviour for MVC, however I cannot think of a way round it. The main issue I am having is redirecting from the rendered action and I understand why I cannot do this.
What I need to know is this: if I can't and shouldn't code my modules in this way, how should I code them so they are independent of the parent view?
I'm still pretty new to AJAX and javascript, but I'm getting there slowly.
I have a web-based application that relies heavily on mySQL and there are individual user accounts that are accessed and the UI is populated with user specific data.
I'm working on getting rid of a tabbed navigation bar that currently loads new pages because all that changes from page to page is information within one box.
The thing is that box needs to reload info from the database, etc.
I have had great help from users here showing that I need to call the database within the php page that ajax is calling.
OK-so pardon the lengthy intro-what I'm wondering is are there any specific limitations to what ajax can call that I need to know about? IE: someone mentioned that it's best not to call script files and that I should remove scripts from the php page that is being called and keep those in the 'parent' page. Any other things like this I need to keep in mind?
To clarify: I'm not looking to discuss the merits/drawbacks of the technology. I'm wondering about specific coding implementation that I need to be aware of (for example-I didn't until yesterday realize that if even if I had established a mySQL connection on the page, that I would need to re establish that connection in my called page as well...makes perfect sense now).
XMLHttpRequest which powers ajax has a number of limitations. I recommend brushing up on the same origin policy. This is a pivotal rule because it limits where AJAX calls can be made.
First, you can't have Javascript embedded in the HTTP response to an AJAX call. That's a security issue.
No mention of the dynamics of the database, but if the data to be displayed in tabs doesn't have to be real-time, why not cache it server-side?
I find that like any other protocol, Ajax works best in tightly controlled conditions. It wouldn't make much sense for updating nearly the whole page, unless you find that the user experience is improved with an on-page 'loader'. Without going into workarounds, disadvantages will include losing the browser back button / history, issues such as the one your friend mentioned, and also embedded resources and other rich content can suffer as well, and just having an extra layer of complexity to deal with in your app. Don't treat it as magic sauce for your app - make sure every use delivers specific results that benefit your client / audience.
IMHO, it's best to put your client side javascript in a separate page and then import it - neater container. one thing I've faced before is how to call xml back which contains code to run such as more javascript - it's worth checking if this is likely earlier on and avoiding, than having to look at evals.
Mildly interesting.
I am trying to find the optimal architecture for an ajax-heavy Django application I'm currently building. I'd like to keep a consistent way of doing forms, validation, fetching data, JSON message format but find it exceedingly hard to find a solution that can be used consistently.
Can someone point me in the right direction or share their view on best practice?
I make everything as normal views which display normally in the browser. That includes all the replies to AJAX requests (sub pages).
When I want to make bits of the site more dynamic I then use jQuery to do the AJAX, or in this case AJAH and just load the contents of one of the divs in the sub page into the requesting page.
This technique works really well - it is very easy to debug the sub pages as they are just normal pages, and jQuery makes your life very easy using these as part of an AJA[XH]ed page.
For all the answers to this, I can't believe no one's mentioned django-piston yet. It's mainly promoted for use in building REST APIs, but it can output JSON (which jQuery, among others, can consume) and works just like views in that you can do anything with a request, making it a great option for implementing AJAX interactions (or AJAJ [JSON], AJAH, etc whatever). It also supports form validation.
I can't think of any standard way to insert ajax into a Django application, but you can have a look to this tutorial.
You will also find more details on django's page about Ajax
Two weeks ago I made a write up how I implement sub-templates to use them in "normal" and "ajax" request (for Django it is the same). Maybe it is helpful for you.
+1 to Nick for pages displaying normally in the browser. That seems to be the best starting point.
The problem with the simplest AJAX approaches, such as Nick and vikingosegundo propose, is that you'll have to rely on the innerHTML property in your Javascript. This is the only way to dump the new HTML sent in the JSON. Some would consider this a Bad Thing.
Unfortunately I'm not aware of a standard way to replicate the display of forms using Javascript that matches the Django rendering. My approach (that I'm still working on) is to subclass the Django Form class so it outputs bits of Javascript along with the HTML from as_p() etc. These then replicate the form my manipulating the DOM.
From experience I know that managing an application where you generate the HTML on the server side and just "insert" it into your pages, becomes a nightmare. It is also impossible to test using the Django test framework. If you're using Selenium or a similar tool, it's ok, but you need to wait for the ajax request to go return so you need tons of sleeps in your test script, which may slow down your test suite.
If the purpose of using the Ajax technique is to create a good user interface, I would recommend going all in, like the GMail interface, and doing everything in the browser with JavaScript. I have written several apps like this using nothing but jQuery, state machines for managing UI state and JSON with ReST on the backend. Django, IMHO, is a perfect match for the backend in this case. There are even third party software for generating a ReST-interface to your models, which I've never used myself, but as far as I know they are great at the simple things, but you of course still need to do your own business logic.
With this approach, you do run into the problem of duplicating code in the JS and in your backend, such as form handling, validation, etc. I have been thinking about solving this with generating structured information about the forms and validation logic which I can use in JS. This could be compiled at deploy-time and be loaded as any other JS file.
Also, avoid XML. The browsers are slow at parsing it, it is a pain to generate and a pain to work with in the browser. Use JSON.
Im currently testing:
jQuery & backbone.js client-side
django-piston (intermediate layer)
Will write later my findings on my blog http://blog.sserrano.com