adamdickinson/react-service

Expose internal application APIs as a service.

react-service's Issues

Return value of hook can be undefined

When calling the hook returned from createService in a component that is not sitting under the service provider the return value of the hook will be undefined.

This makes absolute sense to me (rather than the hook throwing an error for example) and is how vanilla react context works. It's actually ideal because I have components that can be used inside or outside of a service provider, leveraging the service only if they are in its provider.

The only issue is the return type of the hook states it will always return a value, when in reality it can return undefined.

Even if we believe most of the time the hook will return a truthy value, I would prefer we be accurate.

This would be a design-time breaking change for anyone with strict null checking enabled, forcing those consumers to change their code slightly.

Contrived Example:

const LogoutButton = () => {
  const { logout } = useAuth() // If consumer has 
  return <button onClick={logout}>Logout</button>
}

Might need to become something like

const LogoutButton = () => {
  const { logout } = useAuth() ?? {}
  return <button onClick={logout}>Logout</button>
}

Or if they are lazy

const LogoutButton = () => {
  const { logout } = useAuth()!
  return <button onClick={logout}>Logout</button>
}

Or they can be smarter by not rendering the component/rendering it differently if the api isn't provided, etc.

Or if you want to keep the usage simple for consumers who will always define their consuming components within their service providers, then we could offer a way to get a hook for the service that always returns a truthy value or throws an error if the service is not provided.

Thoughts @adamdickinson?

Fix code snippets in README

I was looking over the documentation to refresh myself on usage and I noticed something that didn't look right.

// 1. We define the service
const [NumberProvider, useNumber] = createService(({ max: number }) => {
  const [number, setNumber] = useState<number>()
  return {
    update: () => setNumber(Math.floor(Math.random() * max)),
    number,
  }
})

I think ({ max: number }) => { is meant to be ({ max }: { max: number }) => {.

It looks like the subtle mistake is repeated in the Auth example: const useAuthAPI = ({ serverUrl: string }) => {

When fixing this it would be good to test those entire code snippets to ensure they're correct.

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Feature request: support multiple services with one provider

As mentioned in the README, having many services offered by an app gets a bit intense. Because of how context works, it means we'd be looking at a lot of top-level nesting.

There is another possible option however - shared context.

Implementation Goal

The best APIs are designed for those who use them, not those who build them, so it's worth looking at how we might like to apply a single-provider service structure:

import { Services } from '@adamdickinson/react-service'

import { AuthService } from './services/auth'
import { NoticeService } from './services/notice'
import { ReportService } from './services/report'

const App = () => (
  <Services services={[AuthService, NoticeService, ReportService]}>
    ...
  </Services>
)

import { useAuth } from './services/auth'

const SubComponent = () => {
  const { user } = useAuth()
  return <h1>{user?.name ?? 'Not logged in'}</h1>
}

And if we wanted to, we should be able to expose services at various points in our app:

const App = () => (
  <>
    <Services auth={AuthService}>
      <Services report={ReportService}>
        ...
      </Services>
    </Services>

    <Services notice={NoticeService}>
      ...
    </Services>
  </>
)

The smarter way to handle this would be as follows, but the above illustrates being able to expose many services with only a few providers well:

const App = () => (
  <>
    <AuthService>
      <ReportService>
        ...
      </ReportService>
    </AuthService>

    <NoticeService>
      ...
    </NoticeService>
  </>
)

How do we accomplish this?

A single context seems to be the way...

const ServiceContext = React.createContext()

interface ServicesProps {
  services: Service[]
}

const Services = ({ children, ...services }) => {
  const existingApis = useContext(ServiceContext)
  const apis = { 

    // Carry forward higher-level services
    ...existingApis

    // Add newly defined services
    ...Object.keys(services).reduce((newApis, name) => {
      apis[name] = services[name].useApi()
    }, newApis)

  }

  return (
    <ServiceContext.Provider value={apis}>
      {children}
    </ServiceContext.Provider>
  )
}

Benefits

The simple benefit is that we can now throw in a heap of services without a nesting nightmare, but we could do that without many architectural changes, so why does the above proposal attempt to wrap everything in a single context? Because it allows us to get services talking to each other. Let's say you have a Data service that uses Auth info, and an Auth service that will make use of unauthorised processes in the Data service - this structure will allow us to do this.

More thoughts on the way on this one.

Feature Request: Extended Services

I'm looking to export two service providers from one package - one to handle a normal service, one to handle the mocked variation. Trouble is, both would need to use the same context in order to enable reuse of existing parts throughout the code. That is, I want to be able to switch the provider <MyService> with a mocked version <MyMockedService>.

I'm thinking the following workflow would work well:

const [MyService, useMyService, MyServiceContext] = createService(useMyServiceApi);
const MyMockedService = extendService(MyServiceContext, useMyMockedServiceApi);

They would essentially be the same process, differing only in whether context is provided or created. Alternatively, we could just re-use createService in these ways:

// createService(hook, context?) => [ServiceProvider, ServiceHook];
const [MyService, useMyService, MyServiceContext] = createService(useMyServiceApi);
const MyMockedService = createService(useMyMockedServiceApi, MyServiceContext);

// createServices(hookA, hookB, ...) => [ServiceProviderA, ServiceProviderB, ..., ServiceHook];
const [MyService, MyMockedService, useMyService] = createServices(useMyServiceApi, useMyMockedServiceApi);