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fetch-hoc

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A React higher order component for fetching data from a server and passing the result as props.

Using a HoC for fetching data is easier to understand and master than redux, while at the same time being more consise than writing utilities and extending components.

The resource can be either a string or a function. If the resouce is a function, then the HoC will automatically re-fetch the resouce when the resource URL changes.

This library is super tiny, measuring just over 1kB gzipped, and has no dependencies!

Installation

yarn add fetch-hoc
# or
npm i -S fetch-hoc

If you don't yet use npm or a bundler like webpack, you can get a UMD bundle from unpkg. Simply add one of the following links into your app, and the library will be accessible as FetchHOC on window. Remember to replace [VERSION] with the version you want.

<script src="https://unpkg.com/fetch-hoc@[VERSION]/dist/fetch-hoc.min.js"></script>

Usage

Now it's my job to tell you why this library is cool.

Simply wrap your component in the result of the fetch function to get started. Using this method enables most of your components to be written as functional stateless components, which is great for legibility and testabiliy.

fetch('/some/static/resource')(Component)
// Or
fetch(props => `/some/resource/${props.someProp}`)(Component)

Here is a more complete example:

const FooComponent = props => {
  if (props.error) {
    return <div className="error">{`An error occured! ${props.error}`}</div>;
  }
  if (props.loading) {
    return <div className="loading">Loading...</div>;
  }

  return (
    <div>
      {props.data.map(row => <div>{row.text}</div>)}
    </div>
  );
}

// This feeds the props used in render
fetch('http://foo.com/bar')(FooComponent);

If you need more flexibility in your component, you can also use a function to reduce the URL from the component's props. These props can be redux props if you also have used connect on the component.

// With props from parent
fetch(props => `/user/${props.user}/cart`)(FooComponent);

// With redux
compose(
  mapStateToProps(state => ({ user: state.user })),
  fetch(props => `/user/${props.user}/cart`),
)(FooComponent);

Example: Composition is king

Use composition to compose behaviors upon the props this HoC provides! For example, to add an easily reusable loading icon and error message:

// withLoadingAnimation.js
export default Component => props => (
  props.loading
    ? <YourLoadingComponent />
    : <Component {...props} />
);
// withErrorMessage.js
export default message => Component => props => (
  props.error
    ? <div className="error">{message}</div>
    : <Component {...props} />
);
// FooComponent.js
import withLoadingAnimation from './withLoadingAnimation';
import withErrorMessage from './withErrorMessage';

const FooComponent = ({ data }) => (
  <div>
    <h1>I will only render on a successfully completed fetch!</h1>
    <pre>{data.toString()}</pre>
  </div>
);

export default compose(
  fetch('/foo'),
  withLoadingAnimation,
  withErrorMessage('Failed to fetch that thing'),
)(FooComponent);

Example: Normalizing data

What about if you need a subset of the data, and the entire dataset is not convenient to work with? Simple, add a HoC for that:

const normalize = func => Component => ({ data, ..rest }) => (
  <Component data={func(data)} {...rest} />
);

export default compose(
  fetch('/foo'),
  normalize(data => data.rows.filter(row => row.enabled))
);

API

// @flow

type Options = {
  /* The same as the Fetch API options, see
   * https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
   */
};

fetch(url: string|Function, options: Options|(props: {}) => Options)(component: React.Component)

The HoC will inject the following props:

Prop Type Description
data Object The data returned from the server
error Error Any error that occured while fetching the data
loading boolean Whether the request is currently in flight
success boolean Whether the request was successfully fetched
response Response The full response with headers. Cloned and can be read again
refetchData Function Forces the component to refetch the data without changing the url

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A react HoC for fetching a resource and passing to props

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