class Foo {
    def target
}

class Bar {
    Foo foo = new Foo()
    void do something (Closure c) {
        c.delegate = foo
        c()
    }
}

Bar bar = new Bar()
bar.dosomething {
    target = 10
}

// If a groovy class has a method call(Closure), the object can be passed a closure directly

class Foo {
    def call(Closure c) { ... }
}

Foo foo = new Foo()
foo {
    println 'Hello, world'
}

// This avoids ugly syntax
foo.call({ println 'Hello, world' })