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2 Start and End States - Reference Documentation

Authors: Graeme Rocher

Version: 2.1.0

2 Start and End States

As mentioned before a flow has a defined start and end state. A start state is the state which is entered when a user first initiates a conversation (or flow). The start state of a Grails flow is the first method call that takes a block. For example:

class BookController {
   …
   def shoppingCartFlow ={
       showCart {
           on("checkout").to "enterPersonalDetails"
           on("continueShopping").to "displayCatalogue"
       }
       …
       displayCatalogue {
           redirect(controller: "catalogue", action: "show")
       }
       displayInvoice()
   }
}

Here the showCart node is the start state of the flow. Since the showCart state doesn't define an action or redirect it is assumed be a view state that, by convention, refers to the view grails-app/views/book/shoppingCart/showCart.gsp.

Notice that unlike regular controller actions, the views are stored within a directory that matches the name of the flow: grails-app/views/book/shoppingCart.

The shoppingCart flow also has two possible end states. The first is displayCatalogue which performs an external redirect to another controller and action, thus exiting the flow. The second is displayInvoice which is an end state as it has no events at all and will simply render a view called grails-app/views/book/shoppingCart/displayInvoice.gsp whilst ending the flow at the same time.

Once a flow has ended it can only be resumed from the start state, in this case showCart, and not from any other state.

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