Access the compilation date during compilation in Haxe

Question

I was wondering whether it is possible to access external information - like the current date during compilation.

It would then be possible to do something like this:

class MyInfo {
    private var buildDate:Int = --- AUTOMATICALLY INSERT THE CURRENT UNIX DATE TIME HERE ---;

    public function getInfo():String { // example usage
        return "This library was compiled the " + buildDate;
    }
}

I thought about accessing this information in the compilation bat/sh/make file and then pass it to the compiler, too. (Something similar to "-D".) However the Haxe compiler does not seem to support an argument like:

haxe --main MyInfo --js test.js -SOMEARG date=$(date)

So that I could use the content of the variable date afterwards ...

Answer 1

This can be done with macros (code executing at compile-time).

Your date example is covered in the cookbook, here. You can find more about macros in the haxe manual or in the cookbook.

Edit: Minimal example:

class Test {
  public static function main() {
    trace(getBuildTime());
  }

  public static macro function getBuildTime() {
    var buildTime = Math.floor(Date.now().getTime() / 1000);

    return macro $v{buildTime};
  }
}

The time will be computed at compile-time.