extensions.md

Extensions

nion provides extensions as a way of automatically composing useful functions and meta values out of a resource's data and its basic actions.

The JSON API pagination extension is a great example; it relies on JSON API responses having a particular format for pagination links and composes useful next(), prev(), first(), and last() functions that use the nion-provided GET action to fetch data with those links.

Extensions are dead simple to write; a valid extension is an object with two required functions:

function	description
composeActions	returns an object of functions that are composed of options and a resource's actions and/or data
composeMeta	returns an object of meta values composed of a resource's data

Configuration

Extensions have to be imported and registered with nion's configuration when the store is configured. configureNion takes an extensions option that consists of a map of extensions keyed by the name by which you'll refer to them throughout your application. For instance:

import exampleExtension from './example-extension'
import { configureNion } from 'nion'

const { reducer: nionReducer } = configureNion({
	extensions: {
		myExtension: exampleExtension
	}
})

Read more about configuration here.

Declaration

In a declaration, you can add extensions to a resource by passing a map of extension names and options to the extensions option. Not all extensions require options, so you can pass an empty object as well:

@nion({
    dataKey: {
        someEndpoint,
        extensions: { myExtension: {} },
    },
})

Read more about declaration options here.

In Practice

The resource the nion decorator provides in props looks like this when extended:

// props.nion.dataKey
{
    data,
    actions,
    request,
    extra,
    extensions: {
        myExtension: {
            aFunction: fn(),
            anotherFunction: fn(),
            meta: {
                someValue: true,
            },
        },
    },
}