React Mercury

Overview

This package provides reactivity to Mercury data using a React high order component. It also dispatchs automatically the read method of the Mercury sources.

Connect the desired sources with your components and this library will retrieve the data and re-render your components when corresponds.

Install

npm i @xbyorange/react-mercury --save

Examples

In the next example, the books will be retrieved automatically from server if they are not cached. The component will be rendered again if a new book is added to the collection by another component, or deleted, etc.

Components can be connected to Mercury origins or selectors. The interface is the same in all cases.

Use connect

import React, { Component } from "react";
import { connect } from "@xbyorange/react-mercury";

import { booksCollection } from "data/books"; //booksCollection is a Mercury origin

export class Books extends Component {
  render() {
    const books = this.props.books.value || [];
    const loading = this.props.books.loading;
    const error = this.props.books.error;

    if (error) {
      return <div>ERROR</div>;
    }

    if (loading) {
      return <div>LOADING...</div>;
    }

    return (
      <div>
        <ul>
          {books.map(book => (
            <li key={book._id}>
              {book.title}
            </li>
          ))}
        </ul>
      </div>
    );
  }
}

export const mapDataSourceToProps = () => ({
  books: booksCollection.read
});

export const ConnectedBooks = connect(mapDataSourceToProps)(Books);

Querying Mercury sources using component "props"

In the next example, the component will render only books of author "cervantes", and will request them to the server using the correspondant query (if not cached previously):

export const mapDataSourceToProps = props => ({
  books: booksCollection.ofAuthor(props.author).read
});

export const ConnectedModule = connect(mapDataSourceToProps)(Books);

Connect component to many Mercury sources

The connect function accepts connecting as many sources as you want. Any change on any of the sources will produce a new render of the component:

export const mapDataSourceToProps = () => ({
  books: booksCollection.read,
  authors: authorsCollection.read
});

export const ConnectedModule = connect(mapDataSourceToProps)(Books);

Connect component to specific properties of a Mercury source

You can use the property getters available in sources to pass an specific property to components instead of the full object. This will improve and simplify the usage of props inside the component, because each component prop will be equivalent to an specific source property:

import { connect } from "@xbyorange/react-mercury";

export const BooksList = ({ books, booksLoading, booksError }) => {
  if(booksError) {
    return (<div>Error loading books</div>);
  }
  if(booksLoading) {
    return (<div>Loading books...</div>);
  }
  return (
    <div>
      <ul>
        {books.map(book => (
          <li key={book.id}>
            {book.title}
          </li>
        ))}
      </ul>
    </div>
  );
};

export const mapDataSourceToProps = () => ({
  booksError: booksCollection.read.getters.error,
  books: booksCollection.read.getters.value,
  booksLoading: booksCollection.read.getters.loading
});

export const ConnectedModule = connect(mapDataSourceToProps)(BooksList);

Pass any other type of properties using connect:

The connect function can pass any other types of properties to the Component, not only Mercury sources:

export const mapDataSourceToProps = props => ({
  createBook: booksCollection.create,
  books: booksCollection.read,
  authors: authorsCollection.read,
  myProperty: true,
  anotherProperty: 5,
  isLoadingAny: props.loading || props.anotherLoading || props.anotherOneLoading,
  callback: () => {
    console.log("Callback called");
  }
});

export const ConnectedModule = connect(mapDataSourceToProps)(Books);

Using connect parser function to prepare data synchronously to component

In some scenarios, the component is not prepared to handle asynchronous data, and could fail rendering if, for example, the source value is not already fullfilled because it is loading. A Selector could be used to ensure data in component properties, but, for more specific behaviors related with loading or error properties, a parser function is available in the connector. This function, if defined, will be executed passing all component properties before rendering it, and the returned object will be applied as properties to the Component.

The parser function has to be defined as second argument of the connector:

export const mapDataSourceToProps = () => ({
  books: booksCollection.read.getters.value,
  booksLoading: booksCollection.read.getters.loading,
  authorsLoading: authorsCollection.read.getters.loading
});

export const parseProps = props => ({
  ...props,
  loading: props.booksLoading || props.authorsLoading
});

export const ConnectedModule = connect(
  mapDataSourceToProps,
  parseProps
)(Books);

This parser function should not be used as a replacement to Mercury Selectors. As a good practice, the preference is to use Selectors if possible instead of this function.

Prefetching data on server side rendering

Methods for prefetching data on server side rendering are available too. When data is prefetched in server side, the connect function will pass the value property calculated on server side to the components directly. It will not modify the loading property until the first load on client side is finished (At first client-side load, the resource will not be considered as loading to maintain the server-side value in the component until it finish loading).

It is important to define custom an unique "uuids" for your mercury sources when are going to be read on server side. Otherwise, the readServerSide method will trace a warning if detects duplicated "ids".

Server side data methods and components

• readOnServerSide(source)
  • Alias - addServerSideData
  • Arguments
    • source - <Object> or <Array> of <Objects> Mercury source or sources that should be read when readServerSide method is executed. Can be Mercury origins or selectors of any type, queried or not.
• readServerSide([source])
  • Alias - readServerSideData
  • Arguments
    • source - <Object> or <Array> of <Objects> Mercury source or sources. Will be added to be read with the readOnServerSide method.
  • Returns
    • <Object> This method is asynchronous, and, when resolved, it returns an object containing all server side data ready to be set on the <ServerSideData> context component.
• <ServerSideData data={data} clientSide={true}><App/></ServerSideData> Component that sets the result of the readServerSide method in a context to make it available from all mercury connected children components.
  • Props
    • data - <Object> Object containing the result of the readServerSide method.
    • clientSide - <Boolean> If false, the connect method will not dispatch automatically the read method of the sources marked as "server-side", so, for example, api requests will not be repeated on client side, and data retrieved in server side will be always passed to connected components.

Example of server side prefecth implementation in a Next project:

In the next example, the data of the "myDataSource" mercury source will be fetched on server side and request will not be repeated on client side. The component will be rendered directly with server side data, and no loading state will be set:

// src/home.js
import { readOnServerSide, connect } from "@xbyorange/react-mercury";
import { myDataSource } from "src/data";

readOnServerSide(myDataSource); // source is marked to be read when readServerSide method is executed.

export const HomeComponent = ({data}) => {
  if(data.loading) {
    return <div>Loading...</div>
  }
  return <div>{data.value}</div>
};

export const mapDataSourceToProps = () => ({
  data: myDataSource.read
});

export const Home = connect(mapDataSourceToProps)(HomeComponent)

// pages/index.js
import { readServerSide, ServerSideData } from "@xbyorange/react-mercury";
import { Home } from "src/home";

const Page = ({ serverSideData }) => (
  <ServerSideData data={serverSideData} clientSide={false} >
    <Home/>
  </ServerSideData>
);

Page.getInitialProps = async () => {
  return {
    serverSideData: await readServerSide()
  }
}

export default Page;

Demo

To run a real implementation example in a React app, you can clone the project and execute the provided demo:

git clone git@github.com:XbyOrange/react-mercury.git
cd react-mercury
npm i
npm run build
cd demo
npm i

Now, start mocks server:

npm run mocks

And start the demo app in another shell while mocks are running:

npm start

Contributing

Contributors are welcome. Please read the contributing guidelines and code of conduct.