Discussion about uses for Agent Processes

[OvermindDL1]

@accuser

Specifically, I start my GenServer with a unique id, which in turn starts the Agent with an initial state, perhaps a record loaded via Ecto.

Hmm, I’d probably have stuffed that record into the state (or ‘as’ the state if nothing else).

@accuser

The Agent contains a number of functions that transform its state via get_and_update/3, returning the changes and the new state.

Wait, how do you do this? Adding functions to an Agent basically just means a GenServer, so why not just have it all in a GenServer?

@accuser

1. The Agent is only concerned with what is needed to be done to transform the state of the struct it wraps. It could be a record from Ecto, but could also be a remote service. Nothing needs to know how it works, only that it does.

Yeah, that should be a GenServer, you only add things to that GenServer that relate to messing with its own state.

@accuser

2. The GenServer is only concerned with how the Agent should be transformed.

That could also be another GenServer, but you would not need to keep the transformation for the agent in ‘this’ genserver but could keep it with the data itself in the other genserver directly.

@accuser

3. A complex command might chain several Agent transformations together, and this reduces code duplication.

Hmm, how does this work? Code examples?