Cannot dispatch from effect handler

[chpill]

I started to try writing an effect handler, akin to https://github.com/Day8/re-frame-http-fx

In the code of the handler, there is a call to dispatch that is made...

So we need a way to allow effect handlers to dispatch "locally". The best solution is probably to inject partially applied dispatch! and dispatch-sync! as coeffects.

Currently, all the swapping out of handlers and middleware happpens before the creation of the frank, so we cannot add this coeffect at that moment...

I see 2 solutions here:

• When dispatching an event on frank, systematically add an interceptor at the beginning of the chain that will make sure dispatch! and dispatch-sync! are available as coeffects. The issue with this is that what is stored in the registry will no longer be completely representative of what happens when you dispatch...

• Make the frank hold a registry atom instead of a registry value. Then change the state of that reference to add the new coeffect. Maybe the "local version" of the do-fx interceptor that we inject can be extended with a :before that takes care of that.

I'll have a go at solution 2

[chpill]

Okay, I think I was missing the point a bit. Only effects should be exposed with some dispatch functions, as they are the only ones that should be causing side-effects. So injecting the dispatch functions as coeffects is useless. The do-fx interceptor must provide effects handlers with those dispatch functions.

[chpill]

Note to self: the do-fx interceptor only need to provide the regular dispatch function: As the effect handlers are going to be called during a "dispatching" ie when *handling* is true (see here), they cannot use a synchronous dispatch.

[chpill]

This should be better with https://github.com/chpill/re-frankenstein/commit/c3e28389c840305f1a4686628e1a19c111e08689

[chpill]

I just realized that my comment about synchronous dispatch earlier was in fact mistaken. Many effects will in fact trigger asynchronous behaviors. In that case, it should be possible to do a dispatch-sync!...