@nozbe/watermelondb/src/utils/rx/doOnDispose/index.js

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// @flow

import { Observable } from '../__wmelonRxShim'

// Performs an action when Observable is disposed; analogous to `Observable.do`

export default function doOnDispose<T>(onDispose: () => void): (Observable<T>) => Observable<T> {
  return (source) =>
    Observable.create((observer) => {
      // $FlowFixMe
      const subscription = source.subscribe(observer)
      return () => {
        subscription.unsubscribe()
        onDispose()
      }
    })
}