Sort a collection in grails by date

the sort method takes a closure argument, so the correct call (with implicit parens) is

pics.sort { it.dateCreated }

You can also change the default sort on the association.

In your Picture domain class add:

static mapping = { 
    child(sort:'dateCreated', order:'desc')
}

This is not supported for unidirectional one to many relationships, but works great for bidirectional ones.