release notes for 'modules' release

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# 2013 12 24
## 'Modules' release
### Modules in ScriptCraft
ScriptCraft now has a simple module loading system. ScriptCraft now uses the [CommonJS module contract][cjsmod] - that is - the same module system used by Node.js. All of the javascript code which comes bundled with ScriptCraft has been modified so that it conforms to the CommonJS module system.
### What this means for plugins you've developed using ScriptCraft
If you have written plugins using a previous version of ScriptCraft then you have 2 options...
1. Continue using the previous version of ScriptCraft.
2. Update your plugins to work with the ScriptCraft 'Modules' release.
... Option 2 should be relatively straightforward if you follow these steps...
1. Copy your own custom plugins from the `js-plugins` directory to the new `scriptcraft/plugins` directory.
2. In your javascript code any functions, objects or variables which you want to expose for use by others should be exposed using the special `exports` variable. All other code within your .js files will now be private by default. See below for details on how CommonJS/Node.js modules work.
If you have any questions or concerns or need help converting your existing javascript plugin, contact please post questions on the [ScriptCraft forum][scforum] or open an issue on the [Github project][github]
[github]: http://github.com/walterhiggins/ScriptCraft
[scforum]: https://groups.google.com/forum/?fromgroups=#!forum/scriptcraft---scripting-minecraft
In ScriptCraft, files and modules are in one-to-one correspondence. As an example, foo.js
loads the module circle.js in the same directory.
*ScriptCraft now uses the same module system as Node.js - see [Node.js Modules][njsmod] for more details.*
[njsmod]: http://nodejs.org/api/modules.html
[cjsmod]: http://wiki.commonjs.org/wiki/Modules/1.1.1
The contents of foo.js:
var circle = require('./circle.js');
echo( 'The area of a circle of radius 4 is '
+ circle.area(4));
The contents of circle.js:
var PI = Math.PI;
exports.area = function (r) {
return PI * r * r;
};
exports.circumference = function (r) {
return 2 * PI * r;
};
The module circle.js has exported the functions area() and
circumference(). To add functions and objects to the root of your
module, you can add them to the special exports object.
Variables local to the module will be private, as though the module
was wrapped in a function. In this example the variable PI is private
to circle.js.
If you want the root of your module's export to be a function (such as
a constructor) or if you want to export a complete object in one
assignment instead of building it one property at a time, assign it to
module.exports instead of exports.
#### Module Loading
When the ScriptCraft Java plugin is first installed, a new
subdirectory is created in the craftbukkit directory. If your
craftbukkit directory is called 'craftbukkit' then the new
subdirectories will be ...
* craftbukkit/scriptcraft/
* craftbukkit/scriptcraft/plugins
* craftbukkit/scriptcraft/modules
* craftbukkit/scriptcraft/lib
... The `plugins`, `modules` and `lib` directories each serve a different purpose.
##### The plugins directory
At server startup the ScriptCraft Java plugin is loaded and begins
automatically loading and executing all of the modules (javascript
files with the extension `.js`) it finds in the `scriptcraft/plugins`
directory. All modules in the plugins directory are automatically
loaded into the `global` namespace. What this means is that anything a
module in the `plugins` directory exports becomes a global
variable. For example, if you have a module greeting.js in the plugins
directory....
exports.greet = function() {
echo('Hello ' + self.name);
};
... then `greet` becomes a global function and can be used at the
in-game (or server) command prompt like so...
/js greet()
... This differs from how modules (in NodeJS and commonJS
environments) normally work. If you want your module to be exported
globally, put it in the `plugins` directory. If you don't want your
module to be exported globally but only want it to be used by other
modules, then put it in the `modules` directory instead. If you've
used previous versions of ScriptCraft and have put your custom
javascript modules in the `js-plugins` directory, then put them in the
`scriptcraft/plugins` directory. To summarise, modules in this directory are ...
* Automatically loaded and run at server startup.
* Anything exported by modules becomes a global variable.
##### The modules directory
The module directory is where you should place your modules if you
don't want to export globally. In javascript, it's considered best
practice not to have too many global variables, so if you want to
develop modules for others to use, or want to develop more complex
mods then your modules should be placed in the `modules` directory.
*Modules in the `modules` directory are not automatically loaded at
startup*, instead, they are loaded and used by other modules/plugins
using the standard `require()` function. This is the key difference
between modules in the `plugins` directory and modules in the
`modules` directory. Modules in the `plugins` directory are
automatically loaded and exported in to the global namespace at server
startup, modules in the `modules` directory are not.
##### The lib directory
Modules in the `lib` directory are for use by ScriptCraft and some
core functions for use by module and plugin developers are also
provided. The `lib` directory is for internal use by ScriptCraft.
Modules in this directory are not automatically loaded nor are they
globally exported.