gistfile1.rb

resource_fieldname = field.keys.first
resource_field = @resource.send(resource_fieldname)
resource_field_value = field.values.first
target = resource_field[resource_field_value]
# This if you don't care what it becomes if it's not an array previously
#target = agent.id if target.is_a? Array
# This if you always want it to end up as an array, even if it wasn't previously
#target = agent.id rescue target = []
target.save