Ruby on Rails: Hash#Except and Converting Arrays to Args

Posted by Jeremy Gillick on 21 Jul 2008 10:32 pm in Code

Tonight I was working on rewriting the event creation flow for MixerMixer, the social event community I’ve been building, and couldn’t figure out why the Hash#except method wasn’t working.

My goal was to exclude users who were already invited to the event so they wouldn’t be reinvited when the user edits it. So I have 2 hashes: one with the users that are selected and the other with the users who have already been invited to the event. Should be simple:

# Hash format: user_id => user_id
# current_invites = { 567 => 567, 890 => 890}
# selected_invites = { 123 => 123, 567 => 567, 890 => 890}

add = selected_invites.except(@current_invites.keys)

# Should return { 123 => 123 }
# It actually returns { 123 => 123, 567 => 567, 890 => 890}

As you can see, it returns the full hash and doesn’t remove anything. This will not do.

It tuns out that I missunderstood the Rails documentation. Hash#except doesn’t take in an array of keys to remove it takes in a list of arguments. Here’s a simple example:

add = selected_invites.except(567, 890)
# Returns { 123 => 123 }

Now I needed to figure out how to convert the @current_invites.keys array into an argument list. It turns out to be as easy as adding an asterisk in front of it:

add = selected_invites.except(*@current_invites.keys)
# Returns { 123 => 123 }

Success!

Enjoy.

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Semantic Tab Box v2.0

Posted by Jeremy Gillick on 18 Jul 2007 02:02 pm in Accessibility & Code & Technical

Last year I came up with the original semantic tab box, now I’m improving it. Here are the things I wanted to fix:

  • Keep JavaScript unobtrusive — no inline event handlers and needs to work without JavaScript.
  • Create a standard API that can be easily reused and customized.
  • Make the markup more flexible.
  • Support both vertical and horizontal tabs.
  • Don’t constrain the height of the box — let it expand to the size of the content.
  • Keyboard navigation.

How is this better that other tab boxes out there?

All the tab boxes I’ve seen overcomplicate their solutions. They start with an unordered list of the tab names, followed by the content blocks. With a bit of CSS this looks very nice, but for screen readers the content is disconnected from the tab names and can be very confusing. Just try turning off CSS, you’ll see how horrible this looks:

The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP).

Accessibility is a general term used to describe the degree to which a system is usable by as many people as possible.

Progressive enhancement is a label for a particular strategy of Web design that emphasizes accessibility, semantic markup, and external stylesheet and scripting technologies…

Notice how the content is disconnected from the “tabs” when CSS is disabled (or when being read by a screen reader).

To solve this problem, most people just duplicate the tab name with a header (h2, h3, etc) at the top of each content block and use CSS to hide them from visual users. Here’s an example of what this solution looks like without CSS:

Internet

The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP).

Accessibility

Accessibility is a general term used to describe the degree to which a system is usable by as many people as possible.

Progressive Enhancement

Progressive enhancement is a label for a particular strategy of Web design that emphasizes accessibility, semantic markup, and external stylesheet and scripting technologies…

Sure this works, but why the redundancy? Yuck!

My solution gets rid of the unordered lists and formats the content blocks logically — with header tags.

Enough talk…

…lets get to the examples:

In <head>


<script type=”text/javascript”>
   var tabs = new Tabbox(”editorTabs”)
</script>

In <body>


<div id=”myTabbox”>

   <!– Internet Tab –>
   <div class=”tabPanel selected”>
      <h3><a href=”#interWebTab”>Internet</a></h3>
      <div id=”interWebTab” class=”tabContent”>
         <p>
            The Internet is a worldwide…
         </p>
      </div>
   </div>

   <!– Accessibility Tab –>
   <div class=”tabPanel”>
      <h3><a href=”#accessTab”>Accessibility</a></h3>
      <div id=”accessTab” class=”tabContent”>
         <p>
            Accessibility is a general term used to…
         </p>
      </div>
   </div>

</div>

Pretty simple huh?

Accessibility and Non-JavaScript Support

This new version supports accessibility by using CSS to hide the content divs (<div class="tabContent">) off screen, instead of with the unaccessible display:none CSS property.

These CSS classes are applied with JavaScript, so the content will be viewable if JavaScript is disabled or broken on the page. Try viewing the examples with JavaScript disabled and you’ll see what I mean.

API

To setup the tab box all you need to do is initialize the Tabbox object with the main div ID:

var box = new Tabbox("myTabbox", { header: "h3",
                                   vertical : true,
                                   select: 1,
                                   autosize: true });

All the values in the second parameter are optional:

Name Default Description
header “h3″ The header element used for each tab name. This element cannot be used anywhere else in the content block.
vertical false If the tabs should be oriented vertically. The tabs are setup horizontally by default.
select 0 The tab index to select initially.
autosize true Automatically size the box to the content of the tab.

The code has been commented and layed out logically so updating it with features and enhancements should be easy. Speaking of enhancements…

Advanced Example — Hey Look! Something shiny.

So far the examples have been rather simple and plain so I wanted to create one that was more advanced. This example has a more complex UI, animations and implements the YUI history manager. Now when you change tabs it adds history to your browser and the back button will select the previous tab. Check it out — it’s the Über-Cool, Shiny, Tab Box.

Download

Now that you’ve seen the examples, you can download all the code and use it on your site:
tabbox2.zip (46K)

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ClassAnim & HoverHijax: Keeping Presentation out of Your JavaScript

Posted by Jeremy Gillick on 20 Feb 2007 01:44 pm in Code & Technical

Ever since the dawn of CSS and compliant browsers web developers have been squeezing the presentation layer out of HTML and into external CSS files. It has become a web development battle cry and having a tableless website was worn as your badge of honor. To the web dev elite, having <br> tags in your HTML is a sin punishable by death (or at least severe laughing and poking).

Now we are moving in to the so-called ‘Web 2.0′ era. The time of shiny websites with page refreshes cut down to a select few actions. Animations and special effects compliment the content as it fades in and out of view. Libraries like YUI, Dojo and Prototype are making these things increasingly easy and well supported. But with all this, I feel we’re forgetting something. Where’d the presentation layer go?

When you’re animating a rollover or fading some colors do you stop and thing what you’re doing? You’re putting the colors, dimensions and effects into your JavaScript! The presentation layer that you’ve worked so hard to externalize is leaking into your JavaScript code. This is a slippery slope that we have to prevent now. The presentation layer should remain in the CSS, markup in the HTML and logic in the JavaScript. If you want to change the colors or sizes the elements are morphed into, you should be making those changes in CSS.

This brings me to my solution. I present to you an extension to the YUI animation library that will perform your cool animations from the styles defined in your CSS. I call it ClassAnim.

How it works

  1. ClassAnim starts by reading the styles from the base element.
  2. Then it quickly applies the new CSS class to it, reads the new styles and removes the class. This happens quicker than the user can notice.
  3. Now it compares the styles from both versions, extracts the differences that can be animated, and invokes the animation.

With ClassAnim, when you want to make a color or dimensional change you don’t have to go searching through your JavaScript, you make the change straight in the CSS — the way it was meant to be.

See the demo
(Please note: This API is still beta)

Link Rollovers (HoverHijax)

Here’s a simple implementation for rollovers. You’ll notice that all the links on my site have a fading hover effect on them (try mousing over one). This uses a simplified version of ClassAnim that I call HoverHijax. It only animates colors and does it on mouseover and mouseout. My original prototype would actually honor the :hover pseudo class, but good ‘ol Internet Explorer wasn’t allowing me to get to those styles through JavaScript. The current implementation adds a ‘hover’ class to all links when they are being moused over.

See the demo
(Please note: This API is still beta)

The best thing with HoverHijax is that it follows the Progressive Enhancement (or Hijax) strategy and can easily work with or without JavaScript as long as you use the ‘hover’ class along with a ‘:hover’ pseudo class. The only difference is that without JavaScript it wont have the cool fade effect.

a:hover, a.hover {

   color: #000;

}

Where to Download

You can download these new ‘experimental’ APIs from my subversion repository.

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