gistfile1.rb

def check_delete_constraints
        model.relationships.each do |rel_name, rel|
          debugger if $CASE_DEBUG
          
          #Only look at relationships where this model is the parent
          next if rel.parent_model != model
          
          #Don't delete across M:M relationships, instead use their anonymous 1:M Relationships
          next if rel.is_a?(DataMapper::Associations::RelationshipChain)
          
          children = self.send(rel_name)
          case rel.delete_constraint
          when nil, :protect
            # only prevent deletion if the resource is a parent in a relationship and has children
            if children && children.respond_to?(:empty?) && !children.empty?
              DataMapper.logger.info("Could not delete a #{self.class} a child record exists #{children.first.class}")
              throw(:halt,false) 
            end
          when :destroy!
            if children && children.respond_to?(:destroy!)
              # not sure why but this lazy_load is necessary
              # otherwise children will not be deleted with destroy!
              children.lazy_load
              children.destroy!
            end
          when :destroy
            if children && children.respond_to?(:each)
              children.each{|child| child.destroy}
            end
          when :set_nil
            if children && children.respond_to?(:each)
              children.each do |child|
                child.class.many_to_one_relationships.each do |mto_rel|
                  child.send("#{mto_rel.name}=", nil) if child.send(mto_rel.name).eql?(self)
                end
              end
            end
          end # case
        end # relationships
      end # check_delete_constraints