Grails: Supplying Data to a Global UI Element

Question

Please pardon this newbie question...

In Grails, if I want a partial to be embedded in a layout so that it appears globally, which requires live data, let's say a list of categories, where is the best place to pull the category data to feed it into the view?

I realize this is a very basic question, but I haven't seen this covered in any tutorials yet.

Answer 1

You want to put it in grails-app\views\layouts\main.gsp. That's the default layout that most generated code (and likely most examples that you'll see) will use.

Check out the sitemesh section of the grails documentation.

Answer 2

I think you're trying to ask... "How do I feed the category data to the view when I don't know which action caused the page to render, so the action can't add the data to the model?" If that's so, you can use Groovy code directly in the ${} block, such as:

<g:each in="${ Category.findAll() }" var="cat" />

Note that findAll is added to every Model class, and can be called statically (via the classname, not an instance).

Hope this helps

Answer 3

I started this as a comment to Bill James's answer but I figured it might be longer. Bill suggeseted using groovy code inside ${} to make the template (called partial in Rails) work globally:

<g:each in="${ Category.findAll() }" var="cat" />

But, you should not just add code if you dont feel like it might mess up your tidy xml/html. You can always put it in a closure inside a TagLib and thus make it a Tag. The closure must have no parameters, or an 'attr' parameter, or an 'attr' and 'body' parameters but other signatures are invalid.

class CustomTagLib {

 static namespace = 'cus'

    def categories = { attr, body ->
      g.each( in: Category.findAll(), var: attr?.var ?: 'categories' )
    }

}

Then you can use that tag into the template with the namespace you chose:

<cus:categories />

Personally I prefer using tags since most of the time it is a reusable code, so it's better for not violating the DRY principle.