I find the modelling Clojure data structures very similar to working out what your aggregates roots are for domain-driven design or using a document data store.
I would suggest avoiding using refs in a customer map. In this case, it sounds like customer is your natural aggregate root, so you should embed your subordinate domain objects e.g. contracts directly in the customer map. When you want to add or modify a contract, do it by making a whole new customer map e.g. by using the update-in fn. That way your customer's timeline is a progression of immutable customer states. I would try and reserve references and mutability for multi-threaded situations. My two UGX, Chris On 6 July 2013 02:26, Marc Schneider <snr....@gmail.com> wrote: > Hello, > > I'm trying to implement some business model in Clojure. I have several > years of experience developing OO systems in Java. So it's still very hard > to wrap my head to functional thinking. I hope you can help me with > following questions. > > I need a domain model for customers, contracts and features. > > Customers need to be created and modified. > > You can add one or more contracts to customers. But only one contract can > be active at a given time for a customer. > > Within a contract you can add or remove features. Doing this should create > a bill. A bill is not modifiable after creation. > > The business rules are more complex in reality but I would be happy to get > some inspirations how to implement such a thing with Clojure. > > Functional programming has these immutability building block. But the > domain model I'm thinking of has lots of mutable things that change over > time when I execute the business actions. > > Of course the "history" is also required in the solution. It must be > possible to answer the question "what feature was booked 2 months ago". > > I started a solution where a customer was a map that had some refs to > other maps. Then I had functions to alter the content of the refs. But code > looks ugly and using it doesn't feel functional. > > How should I structure data? Where are the functions? Do I have a bunch of > customer functions that all get a "customer map" or defrecord as first > parameter and maybe other required parameters to do the business work? And > another similar bunch of functions for contracts, features and bills? But > these structures are somehow nested, aren't they? > > If structure will become more clear to me, then the next questions will go > to the "how can I persist and load all my state" direction. I would be very > glad if you could give me hints how I can solve this in a Clojure / > functional way. I want to abstract it so that I can use some placeholder > code in tests without the need for a real database. > > That's quite a lot my brain is thinking about. I hope it's not too much to > find any help here. Maybe there are some example applications out there > where I can find some ideas? All I found yet are only small snippets but no > "working in the field with business meat" :-) > > Thanks a lot in advance for your help. If anything is unclear to you > please tell me and I will try to describe my problems more clearly. > > Marc > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
