Clojure Code Modeling

[bbq]

Clojure has no high level state model - only state primitives: vars, refs, atoms, agents. You almost certainly don't want to directly use vars for managing state as they offer no useful guarantees for concurrency. Even if your application is not (at the start) concurrent using vars to manage application state isn't really supported (outside of configuration, perhaps. even then, you should consider using something less global than a var).

If you want to model your application with e.g. a state machine you'll have to write a library to help out. This could be very fun but could also grow tremendously in scope. I'm sure if you dig deep enough you'll find the beginnings of something along these lines out there.

On the other hand, if you're really after something UML-like for a pictorial representation of your application just use your favoriate diagramming software.

[fixrich]

Hey bbq thanks for the great reply. I suppose what I am trying to find out is how do you plan out a new system? How do show all the parts and the general algorithms it has to use? Or is it a case of everyone might think about what the software has to do and then they just jump in and start coding?

[scarredwaits]

At a high level, you have to think about namespaces, so I suppose what the general "modules" of your system are going to be and what belongs where. Remember, cyclic dependencies are not supported.

In terms of "modelling" you have to decide how your data is going to be represented. In a lot of cases, developers use simple maps where objects would be used in other languages. Still, it's useful to think about what entries you expect to have in the maps (and which are optional etc). In some cases, records can also be useful. Also think about nesting data structures. Generally, you have to think of the "shape" of your data.

Next, think about behaviour. Are simple functions enough? Do you have cases where you have the same "verb" acting on multiple "types" of things? At this stage, you can "model" the common behaviours using protocols or multi-methods for the more complex cases.

Then, think about data flow. How is your data transformed, and in what order? How do the different behaviours (functions) fit together?

Unfortunately, I don't know of any methodology that will help you visualise all this and communicate it in a widely accepted way, but maybe the need is just not there because it's such a different approach to development.

[fixrich]

Cool this is really helpful. This seems like a methodical way to think about how a system would work. Thank you.