08.HOC-for-styling.md

Using HOC for styling

Sometimes there are isolated UI components that only require a minimal amount of state for interaction, and using them as standalone components is sufficient

eg. Interactions in a Carousel

Example: Carousel

The HOC will have a current slide index and have previous and next methods.

// Higher order component
import React from 'react'
// This could be named something more generic like Counter or Cycle
const CarouselContainer = (Comp) => {
  class Carousel extends React.Component {
    constructor() {
      super();
      this.state = {
        index: 0
      };
      this.previous = () => {
        const { index } = this.state;
        if (index > 0) {
          this.setState({index: index - 1})
        }
      };

      this.next = () => {
        const { index } = this.state;
        this.setState({index: index + 1})
      }
    }

    render() {
      return (
        <Comp
          {...this.props}
          {...this.state}
          previous={this.previous}
          next={this.next}/>
      )
    }
  }
  return Carousel
};
export default CarouselContainer;

Using the HOC

// UI component
const Carousel = ({ index, ...props }) => {
  const length = props.length || props.children.length || 0;

  const sx = {
    root: {
      overflow: 'hidden'
    },
    inner: {
      whiteSpace: 'nowrap',
      height: '100%',
      transition: 'transform .2s ease-out',
      transform: `translateX(${index % length * -100}%)`
    },
    child: {
      display: 'inline-block',
      verticalAlign: 'middle',
      whiteSpace: 'normal',
      outline: '1px solid red',
      width: '100%',
      height: '100%'
    }
  };

  const children = React.Children.map(props.children, (child, i) => {
    return (
      <div style={sx.child}>
        {child}
      </div>
    )
  });

  return (
    <div style={sx.root}>
      <div style={sx.inner}>
        {children}
      </div>
    </div>
  )
};

// Final Carousel component
const HeroCarousel = (props) => {
  return (
    <div>
      <Carousel index={props.index}>
        <div>Slide one</div>
        <div>Slide two</div>
        <div>Slide three</div>
      </Carousel>
      <Button
        onClick={props.previous}
        children='Previous'/>
      <Button
        onClick={props.next}
        children='Next'/>
    </div>
  )
};

// Wrap the component with the functionality from the higher order component
export default CarouselContainer(HeroCarousel)

By keeping the styling separate from the interactive state, any number of carousel variations can be created from these reusable parts.

Usage

const Carousel = () => (
  <div>
    <HeroCarousel />
  </div>
);