Require vs. DoFile

[Josh]

The Lua command DoFile() simply executes all the code in the specified file. Require() only executes the code if it has not yet been run in the lua state. With a multi-state system this is not much of an issue, but in a single-state system it has a few ramifications. Let's consider the light_directional.lua class script. Pretend we want to make a change in the class.lua script and have this change seen by re-saving the light_directional script. We make our changes to class.lua and save it. Then we re-save the light_directional script. The changes in class.lua will not be apparent, because the light_directional script calls Require(), not DoFile()! The lua state sees that class.lua has already been run, so it doesn't bother re-running it.

 

There is a way around this. Simply open the integrated script editor and type in "DoFile("Scripts/class.lua")". The script will be re-run. Then you can save light_directional.lua and the changes in class.lua will be apparent.

 

Re-running a script will re-create any tables that were created in that script, and any values added to them will be lost. So if you were to run a script like core.lua, where the class and object tables are created, the results will be unpredictable.

 

Hopefully this helped you to understand better how scripts in the engine work. Remember, you can always save and reload the scene if you think you did something bad to the lua state. Live programming is by its very nature a touchy matter, so if you are doing "heavy" coding you might want to stick to the standalone script editor until you have something stable.