Question

I have two very similar methods in Grails, something like “calculate statistics by os” and “calculate statistics by browser” – effectively both prepare some things, then run a similar query on the DB, then do things with the results. The only part where the methods differ is the query they run in the middle of my method –

def summary = c.list {
    eq('browser', Browser.get(1)) // OR eq('os', OS.get(1))
    between('date', dates.start, dates.end)
}

It occurred to me that the ideal way to refactor it would be to pass in the first line of the closure as a method parameter. Like

doStats (Closure query) {
    ...
    def summary = c.list {
        query
        between('date', dates.start, dates.end)
    }
}

I tried this but “query” gets ignored. I tried query() instead but then the query clause is executed where defined, so this doesn’t work either. I suppose I could just pass the whole closure as a parameter but that seems wrong – the query might also get more complicated in future.

Anyone have any better ideas?

Answer 1

You’re using the criteria DSL which might be different than plain groovy closures.

To do what you’re asking, you can use the method described here –

http://mrhaki.blogspot.com/2010/06/grails-goodness-refactoring-criteria.html

and put your query in to private method.

The more elegant solution for this is to use named queries in grails –

http://grails.org/doc/latest/ref/Domain%20Classes/namedQueries.html

Look at the

  recentPublicationsWithBookInTitle {
       // calls to other named queries…
       recentPublications()
       publicationsWithBookInTitle()
  }

example –