@scaleway/use-dataloader

Tiny hooks to help you manage asynchronous tasks

• Lightweight
• Easy to use
• Easy to integrate with Axios, fetch, or any Promise-based tool

Install

$ yarn add @scaleway/use-dataloader

How to use

Add DataLoaderProvider to your app

Firstly you need to put the context at the top of your App.

import { DataLoaderProvider } from '@scaleway-lib/use-dataloader'
import React from 'react'
import ReactDOM from 'react-dom'
import App from './App'

ReactDOM.render(
  <React.StrictMode>
    <DataLoaderProvider>
      <App />
    </DataLoaderProvider>
  </React.StrictMode>,
  document.getElementById('root'),
)

Now you can use useDataLoader and useDataLoaderContext in your App

cacheKeyPrefix

You can specify a global cacheKeyPrefix which will be inserted before each cache key

This can be useful if you have a global context (eg: if you can switch account in your app, ...)

import { DataLoaderProvider, useDataLoader } from '@scaleway-lib/use-dataloader'
import React from 'react'
import ReactDOM from 'react-dom'

const App = () => {
  useDataLoader('cache-key', () => 'response') // Real key will be prefixed-cache-key

  return null
}

ReactDOM.render(
  <React.StrictMode>
    <DataLoaderProvider onError={globalOnError} cacheKeyPrefix="prefixed">
      <App />
    </DataLoaderProvider>
  </React.StrictMode>,
  document.getElementById('root'),
)

maxConcurrentRequests

You can specify a maxConcurrentRequests which will prevent DataLoader to launch request simultaneously and wait some to finish before start next ones.

This can be useful if you want to limit the number of concurrent requests.

onError(err: Error): void | Promise<void>

This is a global onError handler. It will be overriden if you specify one in useDataLoader

import { DataLoaderProvider, useDataLoader } from '@scaleway-lib/use-dataloader'
import React from 'react'
import ReactDOM from 'react-dom'

const failingPromise = async () => {
  throw new Error('error')
}

const App = () => {
  useDataLoader('local-error', failingPromise, {
    onError: error => {
      console.log(`local onError: ${error}`)
    },
  })

  useDataLoader('error', failingPromise)

  return null
}

const globalOnError = error => {
  console.log(`global onError: ${error}`)
}

ReactDOM.render(
  <React.StrictMode>
    <DataLoaderProvider onError={globalOnError}>
      <App />
    </DataLoaderProvider>
  </React.StrictMode>,
  document.getElementById('root'),
)

useDataLoader

import { useDataLoader } from '@scaleway-lib/use-dataloader'

const fakePromise = () =>
  new Promise(resolve => setTimeout(resolve('test'), 1000))

function MyComponent() {
  // Use a key if you want to persist data in the DataLoaderProvider cache
  const { data, isLoading, isSuccess, isError, error } = useDataLoader(
    'cache-key',
    fakePromise,
  )

  // This is the first time we load the data
  if (isLoading && !data) {
    return <div>Loading...</div>
  }

  // This happen when you already load the data but want to reload it
  if (isLoading && data) {
    return <div>Reloading...</div>
  }

  // Will be true when the promise is resolved
  if (isSuccess) {
    // Will display "test" in the the div
    return <div>{data}</div>
  }

  // Will be false when the promise is rejected
  if (isError) {
    // Will display the error in the the div
    return <div>{error}</div>
  }
}

export default MyComponent

useDataLoaderContext

import { useDataLoaderContext } from '@scaleway-lib/use-dataloader'

const fakePromise = () =>
  new Promise(resolve => {
    setTimeout(resolve('test'), 1000):
  })


function MyComponentThatUseDataLoader({key}) {
  // Use a key if you want to persist data in the DataLoaderProvider cache
  const { data, isLoading, isSuccess, isError, error } = useDataLoader(
    key,
    fakePromise,
  )

  // Will be true during the promise
  if (isLoading) {
    return <div>Loading...</div>
  }

  // Will be true when the promise is resolved
  if (isSuccess) {
    // Will display "test" in the the div
    return <div>{data}</div>
  }

  // Will be false when the promise is rejected
  if (isError) {
    // Will display the error in the the div
    return <div>{error}</div>
  }
}


function MyComponent() {
  const { reloadAll, reload } = useDataLoaderContext();

  const handleReload = (keyToReload) => () => {
      await reload(keyToReload) // Execute the method
    }
  }

  const handleReloadAll = () => {
      await reloadAll()
    }
  }

  return (
    <div>
      <MyComponentThatUseDataLoader key="test" />
      <MyComponentThatUseDataLoader key="test-2" />
      <button onClick={handleReload("test")}>Reload first</button>
      <button onClick={handleReload("test-2")}>Reload second</button>
      <button onClick={handleReloadAll}>Reload all</button>
    </div>
  )
}

export default MyComponent

---

API

useDataLoader

const useDataLoader = (
  key, // A key to save the data fetched in a local cache
  method, // A method that return a promise (ex: () => new Promise((resolve) => setTimeout(resolve, 2000))
  {
    onSuccess, // Callback when a request success
    onError, // Callback when a error is occured
    initialData, // Initial data if no one is present in the cache before the request
    pollingInterval, // Relaunch the request after the last success
    enabled = true, // Launch request automatically
    keepPreviousData = true, // Do we need to keep the previous data after reload
    maxDataLifetime, // Max time before previous success data is outdated (in millisecond)
  } = {},
)

Property	Description
isIdle	true if the request is not launched
isLoading	true if the request is launched or enabled is true and isIdle is true
isSuccess	trueif the request finished successfully
isError	true if the request throw an error
isPolling	true if the request if enabled is true, pollingInterval is defined and the status is isLoading or isSuccess
previousData	if keepPreviousData is true it return the last data fetched
data	return the initialData if no data is fetched or not present in the cache otherwise return the data fetched
error	return the error occured during the request
reload	allow you to reload the data (it doesn't clear the actual data)