multimethods, uberjar, and several namespaces

[Erik Assum]

Hi,

I’ve got a defmulti defined in a namespace and it’s corresponding defmethods defined in other namespaces.
This works fine when working in the repl, but when creating an uberjar, the defmethods in the other namespaces
don’t seem to be found.

I’ve created a minimal case here:

https://github.com/slipset/multitest

There is probably something simple I’m missing, but I cannot seem to find it.

What am I missing?

Erik.

[Jonathan Fischer]

In your minimal case: nothing ever imports multitest.other, so the defmethod never gets loaded.

[Erik Assum]

So, I guess my question then would be, how do I make it load without creating a circular dependency?

Erik. 

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i farta

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[Jonathan Fischer]

Just move your defmulti form out of the namespace that's using it, core in this case.  Like this:

https://github.com/mohiji/multitest/commit/229b064cea42c37173496d96a117805494c8042a

[Erik Assum]

That would work. 

But I would like to argue that the need to require all possible namespaces which may implement a defmethod is a bit, should I say, closed?

This would mean that you can't build a plugin system based on multi methods, right?

Erik. 

-- 

i farta

[Jonathan Fischer]

Just the opposite: it means that, at runtime, you can simply load in a file with your new defmethods and the multimethod gets updated to call through to them dynamically. That's what you see when you're working at the REPL: reloading a file (or typing in a new defmethod directly) is updating your multimethod to call the newer implementation.