I'm looking at grails (2.2), and it's all beautiful and even magical, how it all works. I'm looking at a Controller class which is created with grails create-controller and out of the box it has many methods and properties available, like render(), redirect(), params, request and I presume it goes on and on.
where does all this get wired in? Where in the code/project/framework do I see that render() is made available as a method? And how is it implemented?
As a java developer I'm used to inheritance and code injection and reflection. And in javascript prototypes can do some black magic. But the XXController.groovy is just a standalone object. Is it the name (XXController) or the location (grails-app/controllers?) or is there some injection happening which the IDE can pick up?
As of Grails 2.0+ it's implemented using an AST transformation - previously it was done by adding the methods to the Groovy MetaClass. The benefits of the new approach are that things will be a bit faster and use less memory.
GORM domain class methods now use this approach too (except for dynamic methods like findByFooAndBar which have to be added dynamically to the metaclass) and those have the benefit of being callable from Java since the AST adds the methods to the bytecode. This doesn't help controllers though since they're only called from Grails itself as the result of a web request.
For the gory details, ControllersApi is where the methods are, and they're mixed into each controller class by a combination of ControllerTransformer and the code in the doWithDynamicMethods closure in ControllersGrailsPlugin