Init

The init(Model) function is called first when a Mobius loop is started, and can be seen as a special version of the Update function. It takes a Model just like Update, but it does not have any Event as an argument. It returns a First instead of a Next, the difference being that a First always contains a Model, while a Next sometimes contain nothing or only Effects.

One good way to think of the Init function is as a request to “resume execution from a particular Model”. This means put the loop in a valid state and send off any required Effects to activate it.

An example of putting the loop in a valid state might be that if the old Model was showing an “offline” state, when you restore maybe it would be better to start from a “loading” state and send an Effect to load data. Likewise if the Model already was in a “loading” state, the Init function is responsible for sending an Effect to restart the loading of data. If we don’t do that, then the data won’t ever load, and the user would be stuck in the loading state forever!

Providing a custom Init function is not required, but you need to make sure that this doesn’t lead to the loop ending up in undesired states that the user can’t get out of.

Guidelines for the Init function

The same guidelines apply as for the Update function.