Question

I’ve been googling around for the past 2 hours looking for some simple instructions on how to add my own custom metadata tag in as3 with no success. I’m starting to think that I’m probably not searching for the correct terms.

The Problem

Ultimately, what I want to do is add a custom metadata on a function that takes a function as a parameter and makes sure that the given function has the correct parameters.

I.e. I have the following function:

public function testCallback(callback:Function):void
{
    callback("test");
}

and I want to get a compiler error when I call it like this:

public function doNothing():void
{
    // doing nothing
}

public function someRandomFunction():void
    // ...
    testCallback(doNothing);
}

The way I’m thinking of doing this is by having this metadata:

[Callback(paramName="callback",callbackParams="string")]
public function testCallback(callback:Function):void
{
    callback("test");
}

The extension would run during compilation and, if the function passed does not contain the correct parameters, a compile-time error will be thrown. I THINK by using flex2.compiler.util.ThreadLocalToolkit.logError(path, line, errorMessage); I can accomplish this.

The Search

I’ve been googling for a couple of hours now and couldn’t find a simple tutorial that could get me started. I found some SDK bug reports (SDK-18718, SDK-26041), an unfinished forum post, a tutorial (?) on how to add a custom metadata in FlexBuilder (I’m using FlashDevelop), a not-so-useful answer in StackOverflow and many many more dead ends.

The Help

So far, as far as I could understand, I will use Java to create the extension and then, using a compiler command, I’ll add it into my project. However, I don’t know what do I need to get started.

My two main questions are:
A) What do I need to create the extension in Java? (do I need Flex Builder? Eclipse? what libraries do I need in my classpath?)
B) Once I have compiled this into something (a swc?), how do I include this in FlashDevelop in my AS3 Project?

Thanks in advance!

Update

I’ve been able to create a Java project in eclipse, add the Flex libraries, implement the IMxmlcExtension interface and compile the project into a jar with the correct MANIFEST file. Unfortunately, adding the extra -extension=MyTest.jar in FlashDevelop, did nothing.

In case it is useful, the resulting command line for the compiler was

mxmlc -load-config+=obj\MyProject.xml -debug=true -incremental=true
-swf-version=10 -extension=flex_test.jar -o obj\MyProject634846490611881374

Update 2

Timofei Davydik helped me narrow down the problem. It seems that FlashDevelop is the main problem. Creating an extension and compiling it in command line works. I started a thread in FlashDeveloper’s forums. In case you’re interested, the thread is: -extension compiler option

Update 3

Pilippe is correct, it seems that the problem comes from the fact that FlashDevelop uses Flex Compiler SHell (fcsh). I am now looking into how can I switch compilers.

Answer 1

How to make meta-data tags work in Action Script

Timofei Davydik‘s wrote a quick and simple tutorial in his blog to answer my question, named Flex compiler mxmlc extensions. Forcing compiler language, and helped me a bunch to track down what is the problem (which is why I’m giving him the bounty). In his post, he is using Flash Builder and not FlashDevelop, which brings us to the answer of the next question:

How to program them using Flash Develop

Unfortunately, as Phillipe pointed out, for AS3 projects, FlashDevelop uses the Flex Compiler SHell (FCSH), which doesn’t support meta-data. Since FlashDevelop is open-source, I’ll try (and probably fail) to switch the compiler for testing purposes. For anybody else interested in this, I think this forum post is a good start: [ GIFT ] Try new AS3 compiler (ASC 2.0) in flashDevelop 4.x