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React Context Utils and Observable Hooks
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import React from 'react' | |
/** | |
* Create a React Context that requires a value be provided explicitly (aka. no | |
* default value). Returns the Context Provider + a useContext hook that | |
* encapsulates access to the Context. | |
*/ | |
export function createNamedContext<TValue>(name: string) { | |
const Context = React.createContext<TValue | null>(null) | |
function useContext(): TValue { | |
const value = React.useContext(Context) | |
if (value === null) { | |
throw new Error(`Context value is null for '${name}'.`) | |
} | |
return value | |
} | |
return { | |
Provider: Context.Provider as React.Context<TValue>['Provider'], | |
useContext, | |
} | |
} | |
type ContextValues<TProviders extends React.Context<any>['Provider'][]> = { | |
[P in keyof TProviders]: TProviders[P] extends React.Context< | |
infer V | |
>['Provider'] | |
? V | |
: never | |
} | |
export interface ComposeProvidersProps< | |
TProviders extends React.Context<any>['Provider'][] | |
> { | |
values: ContextValues<TProviders> | |
} | |
/** | |
* Compose multiple Context Providers into one. | |
*/ | |
export function composeProviders< | |
TProviders extends React.Context<any>['Provider'][] | |
>(...providers: TProviders) { | |
return ({ | |
values, | |
children, | |
}: React.PropsWithChildren< | |
ComposeProvidersProps<TProviders> | |
>): JSX.Element => { | |
function child(i: number) { | |
if (i < providers.length) { | |
const Provider = providers[i] | |
return <Provider value={values[i]}>{child(i + 1)}</Provider> | |
} | |
return children | |
} | |
return <>{child(0)}</> | |
} | |
} |
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import React from 'react' | |
import { Observable, Subject } from 'rxjs' | |
export function useObservable<T>(observable$: Observable<T>) { | |
const [value, setValue] = React.useState<T | null>(null) | |
React.useEffect(() => { | |
const sub = observable$.subscribe(setValue) | |
return () => sub.unsubscribe() | |
}, [observable$]) | |
return value | |
} | |
export function useSubject<T>(subject$: Subject<T>) { | |
return React.useCallback( | |
(value: T) => { | |
subject$.next(value) | |
}, | |
[subject$] | |
) | |
} | |
export function useObservableState<T>( | |
subject$: Subject<T> | |
): [T | null, (value: T) => void] | |
export function useObservableState<T>( | |
observable$: Observable<T>, | |
subject$: Subject<T> | |
): [T | null, (value: T) => void] | |
export function useObservableState<T>( | |
observableOrSubject$: Observable<T> | Subject<T>, | |
subject$?: Subject<T> | |
): [T | null, (value: T) => void] { | |
const value = useObservable(observableOrSubject$) | |
const setValue = useSubject(subject$ ?? (observableOrSubject$ as Subject<T>)) | |
return [value, setValue] | |
} |
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