A procedural solution to the problem described in the root project's README.
We chose to represent data with a class holding mutable references to the Organisation fields.
We implement behaviour with static methods that mutate the Organisation instances that
are passed in as the first argument to each of these methods.
Each method asserts that the behaviour applies for the current Organisation state,
using if statements, and it either mutates the state of the Organisation object,
or signals error by throwing an IllegalArgumentException.
The implementation is terse, fast to write and add new behaviours at the cost of making it harder to read and reason about.
There is nothing to remind developers that they should consider the validity
of a new behaviour in every state an Organisation may be, making the addition
of new behaviours a particularly error-prone endeavour. Adding a new state may
also introduce bugs since the assertions of already implemented behaviours may
be too loose in the light of the additional state.
The code is distributed under the GNU GPLv3 license (see COPYING). The choice of GPLv3 is to enforce sharing of improvements to the examples.
The supporting documentation is distributed under the Attribution-ShareAlike Creative Commons License (CC BY-SA).
