Class Consumer

packages/nerv/src/create-context.ts:56–96

  // tslint:disable-next-line: max-classes-per-file
  class Consumer extends Component<ConsumerProps, ConsumerState<T>> {
    static isContextConsumer = true
    state = {
      value: this.getContextValue()
    }

    context: {
      [contextProp: string]: Emiter<T> | undefined
    }

    componentWillMount () {
      const emiter = this.context[contextProp]
      if (emiter) {
        emiter.off(this.onUpdate)
      }
    }

    componentDidMount () {
      const emiter = this.context[contextProp]
      if (emiter) {
        emiter.on(this.onUpdate)
      }
    }

    onUpdate = (value: T) => {
      if (!objectIs(value, this.state.value)) {
        this.setState({
          value: this.getContextValue()
        })
      }
    }

    getContextValue (): T {
      const emiter = this.context[contextProp]
      return isUndefined(emiter) ? defaultValue : emiter.value
    }

    render () {
      return onlyChild(this.props.children)(this.state.value)
    }
  }

  return {
    Provider,