生成代码与文件格式

Question

So my friend and I had an argument that we couldn't resolve. He is writing a general purpose web game library and a map editor. The map editor saves maps as XML, but the map editor can also load a Lua script that exports the details of the map into a Javascript file that looks something like this(he didn't want to post the code, so this is just a snippet with the names changed):

// This probably isn't valid code, but this is the idea of the code generator
(function() {
Game.Level1 = function (state) {
    GameEngine.Group.call(this);
            var Object0 = new Game.Lo(new GameEngine.Point(654 , 975.13), 15, state);
            var slot123 = new GameEngine.TimeSlot(123);        //Start
            slot123.addEvent(new GameEngine.Event(Object0, "x", "current", 15, 200));
...

The idea is that the game library would just run this code instead of having to parse a map file and generate objects on the fly. And the Lua script in the map editor that generates the code could be modified by anyone who wanted to output code in a different language for a different library. (not limited to scripting languages).

I've never heard of this idea, usually i'd expect the map data to be in a standard format like JSON or XML and have the game library parse it.

So given that his library is written in javascript and his map can generate javascript to load files, what are the tradeoffs between running the generated code vs parsing JSON/XML and generating objects from that?

Answer 1

In a generic sense loading the metadata from another script, can give added flexibility to the script generator about how the data is sent, displayed etc. For example, you can have complete math expressions, conditionals etc as the part of the loaded script, that will be parsed and loaded seamlessly by the script parser(interpreter). It might be harder to do the same thing by using XML or JSON ( imagine sending an expression to do Miller Cylindrical Projection via XML, on the fly).

I've seen many situations where the app creates its own scripting language (MAXscript, MEL for Maya) to provide flexibility to the user. These are probably not analogous to your friend's usage of Java script to load metadata. But IMHO, it is a continuous spectrum, starting from metadata text files, to XML,JSON, expression parsing, to full fledged script parsing.

On the other hand, sending complicated scripts, will mean exposing part your code base. Also everyone knows what XML does, and you can expect a non-programmer to use/modify XML files. They are comfortable doing it. They may not be comfortable even reading what they think of as 'programs' or 'scripts'. I've seen this first hand in my company, where the artists were uneasy modify a Lua file. They were comfortable modifying the same information, if it was a simple text file. There might some security issues as well, but I'm really not that familiar with it, so I can't comment.