Flex projects versus Actionscript projects

Question

I have used Flex for about a year before deciding that I would rather develop Actionscript projects.

At the time, it seemed that the framework was too heavy for the kind of work I was dealing with, mainly small web applications , personal sites, portfolios this sort of thing. I also thought that Flex was like a odd hybrid , something targeting seasoned developers but at the same time , adding some function wizards that seemed to target beginners. It seemed overly complexed in some areas and way too basic in others.

On the other hand, the IDE was great , definitely no comparison with Flash CS IDE , so for me it made sense to stick to AS3 projects and use Flex , now FlashBuilder to write my code.

( I need to point out that I'm not a Flash designer, so working with Flash CS was never an option. )

It's been a while since I had a look at the Flex framework and I'm wondering about other Flex/Flash developers position on this issue.

Would you only consider Flex for enterprise level projects? What are the advantages of using one over the other? If you were a Flash developer and moved to Flex, what were your motivations? If you're creating both Flex & Actionscript projects , what are your choice criteria?

Edit:

Although I have received a great answer, I would have been interested to hear from Flex's users, what's your main practical motivation ( as opposed to philosophical :) ) for using Flex over pure Actionscript projects?

Answer 1

Preamble: my experience is primarily with AS3 projects built using a combination of the Flash IDE (FIDE) and Flash Builder 4 (FB4).

I generally prefer pure AS3 (PAS3) projects over Flex projects for the following reasons:

• Size - Flex projects have a much larger minimum size than PAS3 projects. Not suitable for lightweight applications.
• Performance - Flash is not known for its performance, and the layout computations required by a complex Flex application will hammer the end-user's machine. To them, things just end-up feeling slow, non-responsive, or "gunky". Unfortunately, this means that the applications where Flex might be most attractive (i.e. a very complex, adaptable, UI) are the exact places where it stumbles. In the end, you end up writing all this bizarre performance-enhancing optimization code that takes away most of the time you gained from using the built-in layout system.
• Metaphor and Appearance - Flex aims to allow developers to provide end-users with a mature, flexible UI that has the same widgets and widget behaviors that they are used to from native applications. However, due to the performance problems echoed above, the UI never feels quite as nice or responsive as a native app. In addition, it's missing all of the OS-specific peculiarities that end-users are used to and will expect. I don't really understand the motivation to try to emulate native app development or behavior - you're never going to win that fight. Best to make something that stands by itself, which is what most native web applications are doing.
• Flexibility - Dovetailing into the previous argument, Flash's main advantage is its ability to do things that traditional UI widget libraries can't do (at least not very easily). You can make some really, really novel UIs in Flash that just aren't practical to do in native apps without mucking about in OpenGL. Using Flex makes creating novel UI hard again (but it does make creating standard UI much easier, even if it is, in my opinion, sub-standard UI).

I'm curious if anyone has some good examples of Flex being used in any popular, public websites. Grooveshark is the only one that I know about (which is quite nice, but suffers from many of the problems I've outlined, especially on OS X where Flash performance is still poor).

However - it's a tradeoff. Always remember that your time is valuable. Your users might accept a slightly clunky, slightly confusing interface if it lets them do really cool things and that would mean that you could release it now as opposed to later. This brings is to the major downsides of PAS3 development:

• Effort vs. Reward - You have to program all of your own UI. All of it. This can lead to some really, really bloated code where you have to define tons of event listeners for every button you want to create. I don't know how many times I've written various kinds of layout code specific to what I was working on. You can try to write your own abstract classes for these (which I have done), but at some point you're just going to end up re-implementing the Flex framework. Hardly worth your time.
• Development - You can either use just Flash Builder 4, in which case you have to construct every graphical asset by hand in code (which takes forever), or you use the FIDE, in which case you can make lovely artwork but you're stuck with a stone-age code IDE and it takes forrrrrreeeeeeevvvvver to compile anything. Currently I use a hybrid setup where art generated in the FIDE is automatically imported into my FB4 project, but even that is not a perfect solution. They really need to be integrated better.

Another set of things to keep in mind: things that Flash sucks at.

• Flash sucks at text. Do not try to re-implement a web browser inside Flash. Flash is actually quite good at displayed relatively small amounts of text that is unselectable (and, through the use of embedded fonts, is always pixel-perfect), but don't try to create large, expansive text documents inside your Flash project. First, performance will be terrible, and second, users will expect the text to behave the same way all other large text fields do in their native applications (most specifically, their web browser). Selecting text in Flash doesn't feel right because it doesn't feel how your OS does it.
• Flash doesn't play nice with mouse and keyboard input - it constantly fights with the enclosing browser for focus. If your system needs either of those things, users need to click on it first. Don't fall into a trap where people will get confused because their inputs are going to the wrong place.
• Flash is a performance hog - we've all heard this one, and it's not nearly as much of a problem as people like to think, but it does mean that you'll have to put a lot of thought into the performance of your system. Your UI should run at a stable 60FPS when being used and should not use much if any CPU when the user is not interacting with it. If your FPS dips below 60, then your UI will feel slow and gunky compared to native or HTML5 UI. Also make sure to watch for memory leaks.

In the end: user your head. Both approaches are just tools in your arsenal.