(Quick Reference)

6.5.6 Subflows and Conversations - Reference Documentation

Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith

Version: null

6.5.6 Subflows and Conversations

Grails' Web Flow integration also supports subflows. A subflow is like a flow within a flow. For example take this search flow:

def searchFlow = {
    displaySearchForm {
        on("submit").to "executeSearch"
    }
    executeSearch {
        action {
            [results:searchService.executeSearch(params.q)]
        }
        on("success").to "displayResults"
        on("error").to "displaySearchForm"
    }
    displayResults {
        on("searchDeeper").to "extendedSearch"
        on("searchAgain").to "displaySearchForm"
    }
    extendedSearch {
        // Extended search subflow
        subflow(controller: "searchExtensions", action: "extendedSearch")
        on("moreResults").to "displayMoreResults"
        on("noResults").to "displayNoMoreResults"
    }
    displayMoreResults()
    displayNoMoreResults()
}

It references a subflow in the extendedSearch state. The controller parameter is optional if the subflow is defined in the same controller as the calling flow.

Prior to 1.3.5, the previous subflow call would look like subflow(extendedSearchFlow), with the requirement that the name of the subflow state be the same as the called subflow (minus Flow). This way of calling a subflow is deprecated and only supported for backward compatibility.

The subflow is another flow entirely:

def extendedSearchFlow = {
    startExtendedSearch {
        on("findMore").to "searchMore"
        on("searchAgain").to "noResults"
    }
    searchMore {
        action {
           def results = searchService.deepSearch(ctx.conversation.query)
           if (!results) return error()
           conversation.extendedResults = results
        }
        on("success").to "moreResults"
        on("error").to "noResults"
    }
    moreResults()
    noResults()
}

Notice how it places the extendedResults in conversation scope. This scope differs to flow scope as it lets you share state that spans the whole conversation not just the flow. Also notice that the end state (either moreResults or noResults of the subflow triggers the events in the main flow:

extendedSearch {
    // Extended search subflow
    subflow(controller: "searchExtensions", action: "extendedSearch")
    on("moreResults").to "displayMoreResults"
    on("noResults").to "displayNoMoreResults"
}