Skip to main content

Flash for Programmers Part 2: The Display List

The Display List in ActionScript 3 is comparable to the DOM on a web page. Through the Display List you can add and remove your View components.

I am not going to go into too much detail here are there are already many excellent articles about it online (http://www.adobe.com/devnet/flash/quickstart/display_list_programming_as3/) (http://developer.yahoo.com/flash/articles/display-list.html).

Suffice to say you will be calling addChild() and removeChild() quite frequently.

I am going to give you a few practical tips though...

Often (if you are doing truly modular MVC, which I will cover later), you will be firing off notes that may tell you to add and/or remove various components from the display list. You may fire a note which will ask to remove a child which doesn't exist though and this will cause your app to throw a nasty error.

Just like in real life, I find it handy to name my children i.e.

var dialog:Dialog = new Dialog();
dialog.name = "dialog";
this.addChild(dialog);

Later on, you may have some code which removes it.

this.removeChild(dialog);

However, if you aren't sure it will be there there is a better method

if(this.getChildByName("dialog") != null) {
    this.removeChild(this.getChildByName("dialog"));
}

What you are doing is first checking to see this child exists and if so, you can remove it. This should prevent any potential run time errors.
Labels:

Comments

Post a Comment

Popular posts from this blog

Freezing Gems

What is a gem and why would you want to freeze it? In Ruby, there are times when you want to access pieces of functionality that other people of written (3rd party libraries) and you normally have 2 options. You can install a plug in or install a gem. Normally the method you use is determined by which ever is made available by the author. Gems are installed on the host machine and are pretty handy when you want to run things in the command line or else across lots of projects, but their downside is that if you use a gem in a Rails project there is no automatic publishing mechanism when you deploy your site. You will need to log onto the remote host machine and install the gem manually. Plugins are specific to Rails and are similar to gems in that they are also 3rd party libraries. However they are associated with your Rails project as opposed to your machine so they will get posted to the server on a regular deploy. Freezing a gem is the process of transforming a gem into a plug in. Es
24 comments
Read more

Elixir - destructuring, function overloading and pattern matching

Why am I covering 3 Elixir topics at once? Well, perhaps it is to show you how the three are used together. Individually, any of these 3 are interesting, but combined, they provide you with a means of essentially getting rid of conditionals and spaghetti logic. Consider the following function. def greet_beatle(person) do case person.first_name do "John" -> "Hello John." "Paul" -> "Good day Paul." "George" -> "Georgie boy, how you doing?" "Ringo" -> "What a drummer!" _-> "You are not a Beatle, #{person.first_name}" end end Yeah, it basically works, but there is a big old case statement in there. If you wanted to do something more as well depending on the person, you could easily end up with some spaghetti logic. Let's see how we can simplify this a little. def greet_beatle(%{first_name: first_name}) do case first_name d
Post a Comment
Read more

Responsive Web Design

I wanted to go over Responsive Web Design using CSS. In the old days of web development, we had to code to common screen sizes (i.e. 800 X 600, 1024 X 768) and we patiently waited for people to upgrade their computers to have a decent amount of screen real estate so we could design things the way we really wanted. We also took on semi stretchy web layouts etc to expand and contract appropriately. Then about 2 or 3 years ago, Apple released this little device called an iPhone with a 320 X 480 resolution which took the world by storm and suddenly a lot of people were viewing your website on a tiny screen again... Anyways, as it can be difficult to design a site which looks good on 320 X 480 AND 1680 X 1050, we need to come up with some kind of solution. One way is to sniff the client and then use an appropriate stylesheet, but then you are mixing CSS with either JavaScript or server side programming and also potentially maintaining a list of appropriate clients and stylesheets. Also, you
14 comments
Read more