Wells

写React差不多快两年了，几乎每天都可以写出这样的代码

export default class App extends Component {
  state = { loading: true };

  componentDidMount() {
    fetch("https://swapi.co/api/planets/5")
      .then(res => res.json())
      .then(
        planet => this.setState({ loading: false, planet }),
        error => this.setState({ loading: false, error })
      );
  }

  renderLoading() {
    return <div>Loading...</div>;
  }

  renderError() {
    return <div>I'm sorry! Please try again.</div>;
  }

  renderPlanet() {
    const { name, climate, terrain } = this.state.planet;
    return (
      <div>
        <h2>{name}</h2>
        <div>Climate: {climate}</div>
        <div>Terrain: {terrain}</div>
      </div>
    );
  }

  render() {
    if (this.state.loading) {
      return this.renderLoading();
    } else if (this.state.planet) {
      return this.renderPlanet();
    } else {
      return this.renderError();
    }
  }
}

当我们通过fetch请求数据时，我们需要定义一些state来标记请求的状态和结果。

但是这样做会存在什么问题呢？

如果我们想要使用storybook来呈现三种状态下的界面概览，可以做到吗？如果要在不请求数据的情况做单元测试，

一种简单的好的模式，把逻辑和view分开处理

The Container / View Pattern

Class PlanetView extends Component {
  renderLoading() {
    return <div>Loading...</div>;
  }

  renderError() {
    return <div>I'm sorry! Please try again.</div>;
  }

  renderPlanet() {
    const { name, climate, terrain } = this.props.planet;
    return (
      <div>
        <h2>{name}</h2>
        <div>Climate: {climate}</div>
        <div>Terrain: {terrain}</div>
      </div>
    );
  }

  render() {
    if (this.props.loading) {
      return this.renderLoading();
    } else if (this.props.planet) {
      return this.renderPlanet();
    } else {
      return this.renderError();
    }
  }
}

class DagobahContainer extends React.Component {
  state = { loading: true };

  componentDidMount() {
    fetch("https://swapi.co/api/planets/5")
      .then(res => res.json())
      .then(
        planet => this.setState({ loading: false, planet }),
        error => this.setState({ loading: false, error })
      );
  }

  render() {
    return <PlanetView {...this.state} />;
  }
}

Higher Order Components

const withDagobah = PlantViewComponent =>
  class extends Component {
    state = { loading: true };

    componentDidMount() {
      fetch("https://swapi.co/api/planets/5")
        .then(res => res.json())
        .then(
          planet => this.setState({ loading: false, planet }),
          error => this.setState({ loading: false, error })
        );
    }

    render() {
      return <PlanetViewComponent {...this.state} />;
    }
  }
};

export default withDagobah(PlanetBranch);

Render Props common

const App = React.createClass({
  getInitialState() {
    return { x: 0, y: 0 }
  },

  handleMouseMove(event) {
    this.setState({
      x: event.clientX,
      y: event.clientY
    })
  },

  render() {
    const { x, y } = this.state

    return (
      <div style= onMouseMove={this.handleMouseMove}>
        <h1>The mouse position is ({x}, {y})</h1>
      </div>
    )
  }
})s

HOC

const withMouse = (Component) => {
  return class extends React.Component {
    state = { x: 0, y: 0 }

    handleMouseMove = (event) => {
      this.setState({
        x: event.clientX,
        y: event.clientY
      })
    }

    render() {
      return (
        <div style= onMouseMove={this.handleMouseMove}>
          <Component {...this.props} mouse={this.state}/>
        </div>
      )
    }
  }
}

const App = React.createClass({
  render() {
    // Instead of maintaining our own state,
    // we get the mouse position as a prop!
    const { x, y } = this.props.mouse

    return (
      <div style=>
        <h1>The mouse position is ({x}, {y})</h1>
      </div>
    )
  }
})

// Just wrap your component in withMouse and
// it'll get the mouse prop!
const AppWithMouse = withMouse(App)

不足：我们不知道哪个HOC提供了Props； props命名冲突

###Render Props

class Mouse extends React.Component {
  static propTypes = {
    render: PropTypes.func.isRequired
  }

  state = { x: 0, y: 0 }

  handleMouseMove = (event) => {
    this.setState({
      x: event.clientX,
      y: event.clientY
    })
  }

  render() {
    return (
      <div style= onMouseMove={this.handleMouseMove}>
        {this.props.render(this.state)}
      </div>
    )
  }
}

const App = React.createClass({
  render() {
    return (
      <div style=>
        <Mouse render={({ x, y }) => (
          // The render prop gives us the state we need
          // to render whatever we want here.
          <h1>The mouse position is ({x}, {y})</h1>
        )}/>
      </div>
    )
  }
})