3 ms·

It actually makes code a bit cleaner if data has boolean descriptors instead of enums for describing group or partial identity. Easier to check for thing.isSome

It actually makes code a bit cleaner if data has boolean descriptors instead of enums for describing group or partial identity. Easier to check for thing.isSomething than thing.group === someArbitraryValue. Just don’t allow them to enter illegal states or depend on other state. :)

derefr 4y ago
But why not `thing.isSomething()` that's just a pure function defined as `return thing.state in STATES_THAT_ARE_SOMETHING`?
- eurasiantiger 4y ago
  How do you store that in the database? That’s an ORM-level solution, which just hides/black-boxes the ugly code. Also, I already specified ”no illegal state”, which could just as well be ”no state”.
  - derefr 4y ago
    > How do you store that in the database? 1. A very small dimension table, defining the set of flags in terms of the current state: (user_lifecycle_state, is_a, is_b, is_c, ...). Join it to the fact table when you need it. 2. Computed columns in a writable view wrapping the table. 3. Procedures/functions that take the lifecycle state as input, so you can `SELECT u.id, ..., is_active(u.lifecycle_state) AS is_active FROM users`. > which just hides/black-boxes the ugly code I don't see what's ugly about it. The point of defining something as a FSM is that that's a formal definition on the design level, separate from any particular implementation; you can write a single stateless module that defines these predicates in terms of the lifecycle-states on any or all layers of the stack they're needed, and they'll all work the same, because they're all working off a formal definition of the meaning of each state. Compare and contrast: Postgres has an `inet` type for IP addresses. It has a function `family(inet)`, which returns 4 or 6. Your business layer's runtime probably also has a function like that somewhere. They won't necessarily have the same outputs (i.e. your business layer's version might be a pair of predicates `is_ipv4?` and `is_ipv6?`) — but they'll both answer the same way semantically given the same inputs, because they're both working off of a shared formal definition of what an IP address is.
    - eurasiantiger 4y ago
      Thanks for the clarification. The example, however, doesn’t fit reality particularly well given how few implementations actually agree on all possible forms of v4 and v6 addresses.
tempodox 4y ago
Then write a predicate function that wraps this comparison. Extra points if you use a language that can inline the predicate, so you don't have to make a subroutine call for that.

derefr 4y ago

But why not `thing.isSomething()` that's just a pure function defined as `return thing.state in STATES_THAT_ARE_SOMETHING`?

eurasiantiger 4y ago
How do you store that in the database? That’s an ORM-level solution, which just hides/black-boxes the ugly code. Also, I already specified ”no illegal state”, which could just as well be ”no state”.
- derefr 4y ago
  > How do you store that in the database? 1. A very small dimension table, defining the set of flags in terms of the current state: (user_lifecycle_state, is_a, is_b, is_c, ...). Join it to the fact table when you need it. 2. Computed columns in a writable view wrapping the table. 3. Procedures/functions that take the lifecycle state as input, so you can `SELECT u.id, ..., is_active(u.lifecycle_state) AS is_active FROM users`. > which just hides/black-boxes the ugly code I don't see what's ugly about it. The point of defining something as a FSM is that that's a formal definition on the design level, separate from any particular implementation; you can write a single stateless module that defines these predicates in terms of the lifecycle-states on any or all layers of the stack they're needed, and they'll all work the same, because they're all working off a formal definition of the meaning of each state. Compare and contrast: Postgres has an `inet` type for IP addresses. It has a function `family(inet)`, which returns 4 or 6. Your business layer's runtime probably also has a function like that somewhere. They won't necessarily have the same outputs (i.e. your business layer's version might be a pair of predicates `is_ipv4?` and `is_ipv6?`) — but they'll both answer the same way semantically given the same inputs, because they're both working off of a shared formal definition of what an IP address is.
  - eurasiantiger 4y ago
    Thanks for the clarification. The example, however, doesn’t fit reality particularly well given how few implementations actually agree on all possible forms of v4 and v6 addresses.

tempodox 4y ago

Then write a predicate function that wraps this comparison. Extra points if you use a language that can inline the predicate, so you don't have to make a subroutine call for that.