Posts Tagged ‘VisualForce’
Salesforce: JavaScript Remoting – a different way of thinking
Remoting is awesome.
JavaScript Remoting for Apex operates in a very different paradigm from what you might be used to i.e. Visualforce pages have controllers and the two interact through action methods – where this might be a full form submission or some neat AJAX functionality. Remoting also calls controller methods but there is a gaping maw in terms of how the two work under the hood.
I’ve seen a few great articles on the syntax and example usage of JavaScript Remoting for Apex but when I started using it I came across a number domain differences that weren’t documented anywhere. Hopefully my list here will help you in the learning process. The best way to describe the new way of thinking is to examine the features set in contrast to “normal” Apex and Visualforce.
How JavaScript Remoting Differs
- Pass parameters naturally i.e. the call matches the method signature syntactically instead of requiring <apex:param/>.
- Action methods when called in “normal” Visualforce can only return NULL or a PageReference. Remoting allows you to return a wider range of data types, even objects and collections.
- Remoting methods have no access to the view state e.g. if a static variable is initialised to some value (outside the remoting method) a remoting method will see this as NULL unless it is re-initialised in that method! Conversely if a remoting method sets a state variable value the scope of that value is only within that method.
- It’s much faster. I’m building an application at the moment that is 95% backed by JS Remoting and when I show it to other developers they are struck dumb for at least 3 hours because of the speed.
- Neater debugging info in the browser console. Salesforce has done a great job of providing feedback directly to the browser’s console log.
- Each method call gets its own executional/transactional context i.e. fresh governor limits per call!
If I’ve missed anything please let me know and I’ll add it. Viva la knowledge crowdsourcing!
Salesforce: A better way to work with jQuery selectors and Visualforce Component Ids
Irregular Expressions
I get very sad when discussing this particular topic. There are a variety of ways of get Visualforce component Ids and using them in JavaScript but all of them keep me awake at night. Srsly. A commenter on one of my posts got me thinking about how we can do this better and I’ve come up with a way that I think is great. Hopefully you’ll agree.
This post means that my older posts here and here are now retired in favour of this method.
If the world was on the brink of nuclear war with no clear path to peace what could you count on to save the day? Regular Expressions of course. If a meteor the size of Pluto was about to crash into Earth and Bruce Willis was too old to land on it and blow it up what could we count on to rid us of the troublesome rock. Yes that’s right, Regular Expressions. I think you can guess where I’m going with this.
jQuery has the ability to understand very simple regular expressions in it’s attribute selectors. The full documentation can be found here.
To solve our particular problem however the code is simple:
<apex:page>
<head>
<style>
a,span{
display:block;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
jQuery(document).ready(function($){
$('#btn').click(function(e){
e.preventDefault();
console.log('The following element was found when looking for an id of \'output1\':');
console.log($('[id$=output1]')); /* Here's where we're grabbing the element. */
});
});
</script>
</head>
<apex:outputText value="She sells seashells by the seashore." id="output1"/>
<apex:outputText value="Peter Piper picked a pack of pickled peppers." id="output2"/>
<a href="" id="btn">Click me.</a>
</apex:page>
The important part here is the selector $(‘[id$=output1]’) which says, “Find the id value that ends with ‘output1′”. This comes with a warning though! Do not duplicate the Visualforce Id that you give to your elements otherwise this piece of code will find all of them.
When I first wrote this post I used a selector extension library that gives you the full power of JavaScript-based regular expression but Ryan Fritts has rightly shown that the above will deal with 99% of use cases and is simpler. For those of you that need to deal with the extra 1% I’ve implemented a wrapper to regex selector as an example. It does exactly what jQuery is doing above and gives you access to the regex flags as documented here.
Thanks again Ryan!
Client-Side VisualForce Pagination with Pajinate
Pajinated DataTable
Pagination is an essential, and not so easy to implement user interface device that allows the developer to break long lists of items, or one very long item into sub-pages. I love the challenge that pagination brings (who doesn’t really) when developing efficient and reusable server-side code, but this article isn’t about that. Sometimes I need things done quickly, easily, and preferably with as little compromise as possible, and that’s what client-side pagination is all about. Read the rest of this entry »
Friends Romans Country[wo]men
In an attempt to attend DreamForce this year – I will conquer the Atlantic! – I’ve written up a white paper on a set of tools and workflows that I’ve found superb in more ways than one. I’d be happy & ecstatic(hapstatic?) if you could take a gander at my paper and, if it tickles your fancy, give it your vote. The idea itself describes the paper, but I failed to proof read it (and shock! Horror! There is no edit capability) so I’ll post a more refined version here,
Rapid application development is one of the strongest selling points of Salesforce and Force.com Platform; one that I’ve personally experienced time and time again. However, when it comes to translating that beautiful design document into a VisualForce interface, going from the design bits
The design document built from the 960.gs template
to a cross-browser, standards-compliant site prototype can be troublesome and often takes several days… and let’s be honest, potentially weeks. Read the rest of this entry »
Formatting – PageBlockSectionItem, InputField & OutPutField
There are a collection of forum posts asking why VisualForce formatting isn’t being applied correctly to PageBlockSectionItems and/or InputFields, and the answer isn’t immediately obvious so let’s see what we can throw together. Read the rest of this entry »
Salesforce Form Validation Enhanced
I have a dream, and in this dream form-validation is not a chore. All the nasty work is done client-side, and we – the developers – control what an error message says and where it says it! Server-side validation?! Pah, I spit in it’s general direction (but only if no ladies are present). I don’t need or want client-server round-trips.. I want speed, I want beauty, I want control; and I think you do too.
Our end goal: A neat, realtime, client-side validation technique for VisualForce.
Using either inputFields, Apex exception handling and/or the ‘required’ attribute in VisualForce, we have a number of mechanisms to deal with form-validation, but if we’re honest with ourselves, they’re the ten-thousands-spoons when all we need is a knife. I know you’ve heard me singing it’s praise from the rooftops, but yet again, jQuery is here to save the day. Read the rest of this entry »
VisualForce Element Ids in jQuery selectors
I have retired this approach in favour of a much neater solution that can be found here.
This tricky topic had me puzzled for some time and in earlier posts I went the way of using CSS classes to identify DOM elements; but was always a touch dissatisfied with the solution. Not only is it less efficient – valid XHTML pages should only have one element with any Id, although CSS classes can be shared by many elements – but it also feels all hacky ‘n stuff. I’m a bit older now, a bit more experienced and I RTFM. Without further ado, here is why it’s tricky, and how to fix it. Read the rest of this entry »
Masking Input on VisualForce Pages
I am a developer and (at least as often) a (l)user. UI and UX design are important from both perspectives, and it’s important to bear this in mind whilst creating any application. What is this waffle all about? There are some platforms, based in yonder cloud that could tweak the tiniest of features, and make the lives of their users (and administrators) 1 x shed-load better. Until they do that, we’re gonna have to do it ourselves.
Let’s get specific. Typically, validation error messages provided by Apex and VisualForce are only apparent after form is submitted ( or when we’re on the last page of a 39-page wizard ). Of course some cases require that it be this way, but for other cases it’s like my (very) old professor used to say, “Jus’ don’t let em make the mistake in the first place boy *tongue-click*”. Heeding Prof. Swart’s advice, let’s see how we can easily do this. Read the rest of this entry »
Howto: Communicate between template- and inner- pages.
This post is as much about me asking a question as it is about providing a solution, so don’t let me down community. I got your back, but you’ve got to scratch mine too.. A little to the left, ah yeah, that’s it. The topics in question here are page templates, their controllers, and the pages (and the controllers) that use the template. But first let’s start with what I’ve discovered.
I like using page templates, they make my life easier. If I’m creating a site I probably want to have some consistency of navigation, page header, search etc. across all my web pages. So let’s assume I have the following setup:
1. A VisualForce page I use as a template.
2. A controller for this page that handles navigation, searching etc.
3. Several ‘inner’ VisualForce pages that use this template.
4. A controller for each of these pages. Read the rest of this entry »
DML currently not allowed
This almost belongs in my sarcastically titled, “Meaningful Error Messages ..” series, but as it has traceable causes, I thought I’d write something up on it’s most frequent causes (I meant to write this up a few months ago, but it slipped my mind (find it in your heart to forgive an ol’ developer) and now I think it’s time the world knew).
‘DML currently not allowed’, what could that mean? Well it means that DML isn’t allowed. And that it’s not allowed right now, but with the slight promise that given time, it will be allowed. Often in the past, hoping against hope, I kept on pressing that button/link/onclick-area, but the cloud never changed it’s mind. With a sigh I constructed the google-search query and began trundling through the results. Read the rest of this entry »
The Silver Lining 