Grails: Use several closures inside another one

Question

I am creating a criteria depending on several factors. Currently I'm using nested closures in the following way:

Utils.groovy

static def statusAndOrderCriteria = { x ->
    ...
    Utils.commonOrderCriteria.delegate = delegate
    Utils.commonOrderCriteria(x)
}

static def commonOrderCriteria = { x ->
    ...
}

Usage:

Alert.createCriteria().list({
    Utils.statusAndOrderCriteria.delegate = delegate
    Utils.statusAndOrderCriteria(x)
})

I want to use several closures, such as:

Alert.createCriteria().list({
    Utils.firstCriteria(a)
    Utils.secondCriteria(b)
    Utils.statusAndOrderCriteria(x)
})

I don't know how to achieve that. I know that I can't be overwriting the delegate object several times on the same closure.

Answer 1

When you build a GORM criteria query, the delegate of the closure is an instance of HibernateCriteriaBuilder. What you can do is modify your Util closures to accept this builder as a parameter. Then, delegate the method calls to the builder. Here's an example:

class Utils {
    static def statusAndOrderCriteria = { criteriaBuilder, x ->
        criteriaBuilder.eq('foo', x)
        Utils.commonOrderCriteria(criteriaBuilder, x)
    }

    static def commonOrderCriteria = { criteriaBuilder, x ->
        criteriaBuilder.lt('bar', x)
    }
}

Then you can use the static closures in Util like this:

Alert.createCriteria().list({
    Utils.firstCriteria(delegate, a)
    Utils.secondCriteria(delegate, b)
    Utils.statusAndOrderCriteria(delegate, x)
})

Hint: If the closures were not static properties you'd be able to avoid constantly having to pass the delegate, like this:

@groovy.transform.TupleConstructor
class Utils {
    HibernateCriteriaBuilder criteriaBuilder

    def statusAndOrderCriteria = { x ->
        criteriaBuilder.foo()
        Utils.commonOrderCriteria(x)
    }

    def commonOrderCriteria = { x ->
        criteriaBuilder.bar()
    }
}

Alert.createCriteria().list({
    def utils = new Utils(delegate)

    utils.firstCriteria(a)
    utils.secondCriteria(b)
    utils.statusAndOrderCriteria(x)
})