Flexcoders Frequently Asked Questions
Last Updated: 30th May 2005
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Contributors:
Matt Chotin, Steven Webster, Alistair McLeod, Tariq Ahmed, Jeff Tapper,
Peter Farland, Abdul Qabiz, Tracy Spratt, Jesse Warden, Dan Harfleet,
Manish Jethani, Dimitrios Gianninas
1. What is Flexcoders?
2. How does Flexcoders relate to the Macromedia Flex Forum on
www.macromedia.com?
3. Who posts to Flexcoders?
4. Resources to check before asking a question
5. Guidelines for effective question-asking
6. FAQ
1. What is Flexcoders?
Flexcoders is a forum where developers can ask questions about Flex,
FlexBuilder,
and Flex-related technologies (like Cairngorm, FlexUnit and SynergyFLEX).
The
community is made up of everyday Flex developers as well as Macromedia
employees.
However, this is not an official Macromedia-sponsored forum, it is actually
moderated by the folks at iteration::two, a consultancy responsible for
authoring
the book Developing Rich Internet Applications with Macromedia Flex.
2. How does Flexcoders relate to the Macromedia Flex Forum on
www.macromedia.com?
Both the Macromedia Flex Forum and Flexcoders provide help on issues related
to
Flex, and neither is an official support mechanism. Some people monitor
both
forums, some only one. It is up to you to decide where you might have a
better
experience getting a question answered and being able to subsequently help
others.
3. Who posts to Flexcoders?
Everyone who has a question or an answer. Many members of the Flex
development
team read and respond to Flexcoders as well as other Macromedia folks who
monitor
the community.
Some recurring Macromedia folks are:
David Mendels: EVP and GM, highest-level executive in charge of Flex. Lucian
Beebe: Sr. Product Manager, Flex. Matt Chotin, Manish Jethani, Abdul Qabiz,
Gordon Smith, Peter Farland and many more: Engineers on Flex.
Active community members include:
Steven Webster (Technical Director at iteration::two and co-author of
Developing
Rich Clients with Macromedia Flex), Alistair McLeod (Development Director at
iteration::two and co-author of Developing Rich Clients with Macromedia
Flex),
Jesse Warden (JesterXL - Flash badass playing with Flex), Tracy Spratt
(long-time
member, holder of all knowledge related to 32K limits), Jeff Steiner
(maintainer
of www.flexauthority.com), Tariq Ahmed (maintainer of www.cflex.net), Jimmy
Gianninas (long-time member, developer at Optimal Payments).
And so many more!
4. Resources to check before asking a question
The Flexcoders Mail Archive (better searching than YahooGroups):
http://www.mail-archive.com/flexcoders%40yahoogroups.com
http://www.cflex.net/showfaq.cfm
http://livedocs.macromedia.com/flex/15/asdocs_en/index.html
http://www.macromedia.com/go/flex15_java_livedocs
http://www.macromedia.com/cfusion/knowledgebase/index.cfm
http://www.cflex.net
http://www.flexauthority.com
http://www.macromedia.com/devnet/flex
http://coenraets.com
http://weblogs.macromedia.com/mxna/
http://www.google.com
The Book "Developing Rich Clients with Macromedia Flex" (check your favorite
bookstore)
5. Guidelines to effective question-asking
Include a useful subject; this will help people find their own questions and
answers later.
Explain what you are trying to accomplish.
Explain the error (include compilation errors or a description of the
runtime
behavior).
Be prepared to break your problem down into a simpler scenario in case
someone
wants to try to debug the code themselves. Remember, private web services
are
inaccessible; you may need to create some dummy data to emulate problems.
Phrases to avoid:
"URGENT" (we all have deadlines, no one is intentionally delaying a response
to
you)
"Please send code" (this is very frustrating to read as it implies you
aren't
interested in learning anything on your own. Where code is appropriate you
can
expect someone to provide it, but in many cases you will learn more by doing
it
on your own with appropriate guidance. It may be that you're on a deadline
and
just want to finish, but many of those who respond regularly would prefer to
"teach you to fish" so that you can answer your own questions next time and
even
help out others).
6. Mini-FAQ
Q: Can I mail Matt, Manish, Abdul, Pete, Gordon, iteration::two, or anyone
else
for that matter off-line with my question?
A: Please don't! If someone is capable of answering your question on-list
please
believe that it will be done. Everyone on the list has full-time jobs doing
their own work and often answer flexcoders on their own time; mailing them
off-
list doesn't endear you to them. If no one answers on-list in a reasonable
amount of time (24 hours) you can try to rephrase the question and perhaps
include more detail (including a version of the problem that someone can run
without doing any setup on their own machine).
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Q: When is Flex 2.0 coming out, what will be in Flex 2.0?
A: Macromedia has not announced the schedule for Flex 2. Details of the
release
are expected to come in the next few months, but for now there is no real
public
information about features or anything else.
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Q: What does "Branch between ... and ... around line ... exceeds 32K span"
mean
and how do I get rid of it?
A: Don't panic. Your app is NOT too big for Flex to handle. True, the 32k
limit
is a real Flash Player limitation to the size of certain structures like if
blocks and for loops. But you don't really care about that right now,
because
you don't have any direct control over those things. Here is some
information
that will help you get back to coding:
There are two main reasons you might the 32k issue. The primary cause, and
the
one to address first, is the architecture of your application code. The 32k
error message asks you to "refactor" your code. Refactoring is essentially
the
process of modifying the structure of your source code while keeping the
same
functionality. In the Flex world, this means moving some parts of the code
out
of a main file and into separate components. One way to do this is to use
custom
mxml components. So instead of, say, having several hundred lines of mxml
in a
child container of a ViewStack, you put that mxml code into its own
component
file, and have a single line in the ViewStack to reference it. Do that for
all
the ViewStack children and 1000 lines of code can become 30. Decreasing the
total
number of visually rendered mxml tags in a single file will help avoid the
32k
limit. Another type of refactoring is to move ActionScript code into its own
class. Important note! Just putting the AS code into a file and then using
the
#include directive or the <mx:Script source="filename"> to include the code
will
NOT help with the 32k problem. You MUST create a true AS class that
contains the
functionality. Around two thousand lines of mixed mxml and AS code and you
are
in danger of the 32k error. I have not found an upper limit whatsoever to
code
length in a class.
The second cause of the 32k error is not your fault. During compile, Flex
generates AS code out of your mxml source. Then it compiles that into the
Flash
swf. In that process it makes decisions on how to break up your source and
generate the AS class code. In Flex version 1.5, it doesn't always make the
right decision, and the result is the 32k error. IF you are confident that
you
app is already efficiently "refactored", and you suspect you might be at one
of
these boundary conditions, first try compiling the app with ?debug="true" in
the
url. If the app compiles, then you are surely at a boundary condition.
What is
happening is that debug adds code to your source during generate/compile.
This
additional code causes Flex to change the structure of the AS classes so
that the
32k limit is not hit. Hmm, more code? Yeah. Try just adding 50 or so
lines of
code, even if it is bogus. Usually, this will get you working. Now, when
you
add more real code go on and remove the bogus stuff, you don't want it in
your
production code!
A final hint. After hitting a 32k error, and trying one of the above
solutions,
if you still get the error, delete the temporary generated as code. It is
located in ..\MyAppServer\flex(flexroot or contextroot)\WEB-
INF\flex\generated\*. You can delete all the folders safely (make sure to
restart your Flex server).
This can be an aggravating and somewhat scary problem, and it always seems
to
happen just before an important demo. Just use good, modular design, and
remember the bogus code trick. Macromedia has stated a committment to
improving
this situation in the next release.
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Q: What does "Warning: Changes to unknown property, ..., will not be
detected"
mean and how do I get rid of it?
A: Generally speaking, binding needs type information to set up its change
detection functionality, and anything that hides this info can cause this
problem. Don't use mx.core.application.application.myVariable in binding.
If
you are passing a reference to some component into another component via
public
properties, type the property variable definition as specifically as
possible.
When using "dot.down" notation to specify a property in an object or model,
cast
it to a type: text="{String(myObject.whatever.firstName)}"
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Q: Is there a Rich Text Editor?
A: With the current Flex 1.5 component set, there is no Rich Text Editor
unfortunately. There are some limitations in the current Flash Player that
make
such an editor difficult though there are implementations out there people
have
used. Macromedia has heard many requests for a Rich Text Editor and has
indicated there might be better support in a future release.
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Q: How to run Flex as a Service?
A: Flex is not a server that you deploy and run, it is simply deployed as
part of
your web application. So whatever web container you are using, either
Tomcat,
JRun 4, WebLogic, etc... so long as you can run any of those as services,
then it
will work. To learn how to deploy Tomcat, JRun 4 or any other Java server as
a
service, please refer to the appropriate documentation for the server you
are
using.
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Q: Does Flex work on my platform?
A: Probably, search the archives if you have a specific question about your
platform before posting to the list.
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Q: How do I get Flex to query my database?
A: Flex does not have any native database integration functionality. you
will
require some server-side tier that will do the database access and send the
data
back to Flex via one of three protocols:
* RemoteObjects: Fastest. communicates with server side EJB's or POJOs using
AMF, a binary, compressed format.
* HTTPService: uses HTTP protocol. Sources can be JSP, ASPx,.NET, files, any
url
that returns HTTP.
* WebService: Slowest. Uses SOAP protocol. Sources can be .Net, or any
WebService.
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Q: I'm sending my request, and I see the data traffic in the command window,
but
the result is always empty.
A: You are probably trying to read the result immediately after the send(),
right, expecting synchronous behavior? You can't do this. See "How do I
make
synchronous data calls?"
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Q: How do I make synchronous data calls?
A: You CANNOT do synchronous calls. You MUST use the result event. No, you
can't
use a loop, or setInterval or even doLater. This paradigm is quite
aggravating
at first. Take a deep breath, surrender to the inevitable, resistance is
futile.
There is a generic way to handle the asynchronous nature of data service
calls
called ACT (Asynchronous Call Token). Search for this in Developing Flex
Apps doc
for a full description, but here it is in a nutshell. This example uses
HTTPService but will be similar for RemoteObject and WebService:
* First, create a function to handle the data return, like "onResult()"
* In the HTTPService tag, put this function name in the "result" property,
passing in event. <mx:HTTPService id="mxdsGetData"
result="onResult(event)"
...>
* Invoke the call in script:
//invokes the call to the HTTP data service
var oRequestCallbject = app.mxdsGetData.send(oRequest);
//we will use this string value in the result handler.
//Yes, you CAN set this AFTER you invoke send()
oRequestCall.MyQueryId = "WhateverIWanttoUseToIdentifyThisCall" ;
* In the result handler, which will be called every time the data service
call
returns, you identify what the returned data contains like this:
var callResponse = oEvent.call; //get the call object
//gets the value of this property you set in the call
var sQueryId = callResponse.MyQueryId;
//will be "WhateverIWanttoUseToIdentifyThisCall";
trace(sQueryId);
You can use this sQueryId value in a switch to do the correct processing.
Alternatively, you can pass reference to a handler function directly.
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Q: When I have only a single record, it does not display in my DataGrid
A: This is a known issue that is caused by Flex's inability to differentiate
between an object and an array with a single row. the solution is to ALWAYS
use
"toArray()". Here are some examples:
In MXML:
<mx:DataProvider>
{mx.utils.ArrayUtil.toArray(modelAccidents1.accidents.accident)}
</mx:DataProvider>
And the inline format:
dataProvider={mx.utils.ArrayUtil.toArray(testSrv.result.result.error)}
And in ActionScript:
myControl.dataProvider =
mx.utils.ArrayUtil.toArray(testSrv.result.result.error)
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Q: I have two alerts in my code, but they are displaying in reverse!
A: Actually, it is worse that that. Alerts, and "Modal" pop-up windows are
not
truly modal. They prevent user interaction with the interface, but they do
NOT
block code execution. What is happening is that both alerts are displaying,
and
the second one is on top of the first. The way to get the behavior you want
is
to use events and handlers. Your code must display the alert or modal
pop-up,
the end. When the user dismisses the prompt, you then complete the
processing.
You should be able to find some examples if this on one of the sites listed
in
"Resources"
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Q: The columns in my DataGrid are in some strange order!
A: The order is typically the reverse of the order in which they were added.
If
you need a specific order, specify that and many other good things by using
DataGridColumn tags. See the docs.
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Q: Can I embed HTML in my Flex application?
A: Flex supports a limited subset of HTML in its TextArea and some other
text-
related classes. There is also a new article by Christophe on his blog
discussing how to fake HTML with an IFRAME (
http://coenraets.com/viewarticle.jsp?articleId=95).
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Q: How can I make FlexBuilder faster?
A: In order to improve FlexBuilder performance, it is best to disable the
"Design
View". This can only be done in FlexBuilder 1.5 and to do so, please follow
these
steps:
* Select "Preferences" under the "Edit" menu
* In the "General" section, remove the check mark next to "Enable MXML
Design
View"
* click on "OK"
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Q: Flex Builder debug does not stop at breakpoints in components
A: The safest way to set breakpoints in component files is to use the Files
list.
Start the debugging session, nav you app to where you want to start
debugging.
Click the "Files" button on the Debug Toolbar, or go Menu Debug\Files.
Select
the component you want, usually the .mxml or .as files. The list strips out
underscores in filenames, and can be very long, but this method always
works. FB
will open a temporary file, set the breakpoints, and away you go.
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Q: Are there frameworks available for Flex?
A: Yep!
Cairngorm: http://www.iterationtwo.com/open_source_cairngorm.html
FlexUnit: http://www.iterationtwo.com/open_source_flexunit.html
SynergyFLEX: http://www.mossyblog.com/archives/473.cfm (this link is for
1.0.0a)
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Q: When will Flex for .NET be available?
A: Macromedia has not announced a date.
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