Top 10 things new Flex developers should know

Top 10 things new Flex developers should know
By Michael Portuesi | Published: November 27, 2009
While helping a coworker get started with Flash and Flex development, I thought it would be a good time to cover the list of things that I have found pretty essential to know about Flex development, coming into it as a new developer.
Some of these items are simple details that you need to know. Others point to profound differences between Flash/ActionScript/Flex and other development environments.
Before you start
If you know HTML/CSS development, and some JavaScript, but nothing about ActionScript or Flex, you should really take the time to understand what object-oriented programming means, as ActionScript is a true object-oriented language, and Flex is an object-oriented framework.  The same advice applies if you have been doing pure timeline-based Flash development without getting much into the ActionScript stuff.
Doug Winnie of Adobe has produced an excellent article addressing this topic.  Additionally, he offers a series of free online video tutorials to get you started with ActionScript development from the perspective of a Flash developer.
1. Things happen asynchronously, even the simple stuff
Flex is a very asynchronous framework.  What does ‘asynchronous’ mean?  Basically, it means that you can’t really depend upon something happening right when you invoke the call to it in your code.  Instead, the actual consequences of an assignment, or a call to a method on an object, might happen at some arbitrary time in the future.
This is not just the case when you call a remote HTTP webservice from your Flex application; it’s also the case when you do something as simple as setting the dataProvider property for a user interface control such as a DataGrid. Behind the scenes, DataGrid performs all kinds of work that doesn’t necessarily occur at the time your code make the assignment, and you don’t neces