Configuration
Overmind is based on a core concept of:
{ state, actions, effects }
This data structure is called the configuration of your application. If it is a simple application you might have a single configuration, but typically you will create multiple of them and use tools to merge them together into one big configuration. But before we look at the scalability of Overmind, let’s talk about file structure.
Namespaces
As your application grows you start to separate it into different namespaces. A namespace might be closely related to a page in your application, or maybe it is strictly related to managing some piece of data. It does not matter. You define the namespaces of your application and they probably change over time as well. What matters in the context of Overmind though is that each of these namespaces will contain their own state, actions and effects. So imagine a file structure of:
In this structure we are splitting up the different components of the configuration. This is a good first step. The index file acts as the file that brings the state, actions and effects together.
But if we want to split up into actual namespaces it would look more like this:
In this case each namespace index file bring its own state, actions and effects together and the overmind/index file is responsible for bringing the whole configuration together.
The state file
You will typically define your state file by exporting a single constant named state.
The actions file
The actions are exported individually by giving them a name and a definition.
The effects file
The effects are also exported individually where you would typically organize the methods in an object, but this could have been a class instance or just a plain function as well.
You might find it more useful to define a single effects file at the root of your application and rather create a file for each effect.
Bring it together
Now let us export the state, actions and effects for each module and bring it all together into a namespaced configuration.
We used the namespaced function to put the state, actions and effects from each namespace behind a key. In this case the key is the same as the name of the namespace itself. This is an effective way to split up your app.
You can also combine this with the merge tool to have a top level namespace.
Even though you split up into different namespaces each namespace has access to the state, actions and effects of the whole application. This is an important feature of Overmind which allows you to scale up and explore the domains of the application without having to worry about isolation.
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