import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
import { interval } from 'rxjs'

class RenderObservable extends Component {
  state = {
    value: null
  }

  mountObservable() {
    if (!this._subscription && this.props.observable != null) {
      this._subscription = this.props
      .observable
      .subscribe(value => this.setState({ value }))
    }
  }

  componentDidMount() {
    this.mountObservable()
  }

  componentDidUpdate() {
    this.mountObservable()
  }

  componentWillUnmount() {
    this._subscription.unsubscribe()
  }

  render() {
    return this.state.value
  }
}

class App extends Component {
  _obs$ = interval(1000)

  render() {
    return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h1 className="App-title">Welcome to React</h1>
        </header>
        <RenderObservable observable={this._obs$} />
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
      </div>
    );
  }
}

export default App;