> but this seems like it would solve your > problem. You basically don't want a MessageDigest to be created if one > with the same code exists for a specific data_file_id Close but broken in a concurrent environment. Always try and fix these problems in the data model first.
If you include the data_file_id as a property you can make it part of the key class MessageDigest include DataMapper::Resource property :data_file_id, Integer, :key => true property :code, Enum[:md5, :sha1, :crc32], :key => true property :value, String, :required => true, :length => 255 belongs_to :data_file validate_is_unique :data_file_id # I don't think you get this auto- magically end On Feb 18, 2:01 pm, casual <kab...@gmail.com> wrote: > I feel like there is an easier way to do this, like :unique > => :key_uniqueness_is_based_on > > class DataFile > include DataMapper::Resource > property :id, Serial > property :contents, Text > has n, :message_digests > end > > class MessageDigest > include DataMapper::Resource > property :code, Enum[:md5, :sha1, :crc32], :key => true > property :value, String, :required => true, :length => 255 > belongs_to :data_file > before :create, :check_unique_code > > protected > def check_unique_code > MessageDigest.first(:code => code, :data_file_id => data_file_id) > end > end > > On Feb 16, 1:33 pm, franco <flazzar...@gmail.com> wrote: > > > > > I want a DataFile to have at most one MessageDigest of a certain code. > > I've tried a bunch of combinations of :key and :unique_key etc but i > > cant seem to get it right. > > > if i were to do this in a SQL DDL i'd make data_file_id and code a > > composite key. how can i make it work in datamapper? > > > example models: > > > class DataFile > > include DataMapper::Resource > > property :id, Serial, :key => true > > property :contents, Text > > has 0..n, :message_digests > > end > > > class MessageDigest > > include DataMapper::Resource > > property :code, Enum[:md5, :sha1, :crc32] > > property :value, String, :required => true, :length => 255 > > belongs_to :data_file > > end -- You received this message because you are subscribed to the Google Groups "DataMapper" group. To post to this group, send email to datamap...@googlegroups.com. To unsubscribe from this group, send email to datamapper+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/datamapper?hl=en.
