Howto:Load a Nasal file at runtime

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Status: Planning

Last updated: 12/2010

Authors: Hooray

References:

This tutorial will document all the steps involved in loading a Nasal file at runtime, Nasal is FlightGear's scripting language.

This tutorial is based on Howto: Create a new Nasal module, you should fully understand that one first.

• create a new plain text file under $FG_ROOT/Nasal/MODULE.nas
• replace MODULE with the name for your new module (for example, use "test")
• paste the following code into this file using a text editor (such as notepad on Windows)

 # test.nas (save in $FG_ROOT/Nasal)
 var loader = func {
   io.load_nasal("loadme.nas.txt");
 }
 
 _setlistener("/sim/signals/nasal-dir-initialized", loader);

This piece of code defines a new function named "loader" that just invokes the io.load_nasal() function to load and execute a Nasal script, the filename being "loadme.nas.txt" (the .txt. extension is just to prevent the file from being loaded during startup).

The _setlistener call at the end of the snippet waits for the Nasal system to be initialized before the "loader" function gets called.

Then create another file containing:

 # loadme.nas.txt 
 print("loadme.txt loaded");