How to call a Grails service in a view?

Question

Simple question : I have a service class (let's say helpersService) and a method def constructURI(params). How can I call this method from a template view.

I have tried the following code without success

<% def helpersService  = new HelpersService() // or def helpersService
%>
<img src="${helpersService. constructURI(params)}"/>

But I get the following result:

No signature of method: com.HelpersService. constructURI() is applicable for argument types...

or (in case I use def helpersService)

Cannot invoke method constructURI() on null object 

Any ideas?

Answer 1

Services are not intended to be used inside views. You could create a TagLib where you can get a reference to the service via dependency injection.

Answer 2

An easier method, assuming your view is being rendered by a Controller, is to just pass a reference to the service from the action to the view within the model, i.e.:

class someController {
  def someService
  def someAction = {
    render(view: 'someView', model: ['someService': someService])
  }
}

It can then be used as you would expect within the view. For a template rendered by a view, obviously you need to pass the reference to the template as well. Just to be clear though, S. Puchbauer is right; services are not really supposed to be used within Views, and you may experience difficult to diagnose problems, especially related to transactions and the Hibernate session.