How do you share common methods in different grails controllers?

Question

Currently when I need to share a method like processParams(params) between different controllers, I use either inheritance or services. Both solution has some inconvenients :

• With inheritance, you cannot use multiple inheritance which means that you need to have all of your controller utility methods in one place. And also, there is a bug in grails that does not detect any code changes in Base Controller classes in development mode (you need to restart the app)
• With services, you don't have access to all injected properties like params, session, flush...

So my question is : is there any other way to use some common methods accessible for multiple controllers ?

Answer 1

One option I like is to write the common methods as a category, then mix it into the controllers as necessary. It gives a lot more flexibility than inheritance, has access to stuff like params, and the code is simple and understandable.

Here's a tiny example:

@Category(Object)
class MyControllerCategory {
    def printParams() {
        println params
    }
}

@Mixin(MyControllerCategory)
class SomethingController {

    def create = {
        printParams()
        ...
    }

    def save = {
        printParams()
    }
}