hash_plus
Extensions to the Ruby Hash class
my_vehicle = {
:make => 'Subaru',
:model => 'Forester',
:year => 2525,
}
my_vehicle.requires_fields(:make, :model) # No errors
my_vehicle.requires_fields(:mileage) # Raises Argument error
my_vehicle[:mileage] = nil
my_vehicle.requires_fields(:mileage) # Raises Argument error
my_vehicle[:mileage] = 40_000
my_vehicle.requires_fields(:mileage) # No errors