MobX를 공부하자 (2)

import React, {Component} from 'react'

import {observable} from 'mobx'
import {observer} from 'mobx-react'

// @observer 데코레이터가 장착되어 있는 리액트 컴포넌트는
// @observable로 되어 있는 모든 것들을 rendering 하는 와중에 사용한다.
@observer
class Counter extends Component {
  // @observable 은 @obsever컴포넌트에게 변화를 감시해야 하는 값을 알려준다.
  @observable count = 0

  handleDec = () => {
    this.count--
  }

  handleInc = () => {
    this.count++
  }

  render() {
    return (
      <div>
        Counter: {this.count} <br />
        <button onClick={this.handleDec}>-</button>
        <button onClick={this.handleInc}>+</button>
      </div>
    )
  }
}

export default Counter

import React, {Component} from 'react'
import ReactDOM from 'react-dom'

import {observable} from 'mobx'
import {observer} from 'mobx-react'

const appState = observable({
  count: 0,
})

appState.increment = function () {
  this.count++
}

appState.decrement = function () {
  this.count--
}

@observer
class Counter extends Component {
  render() {
    return (
      <div>
        Counter: {this.props.store.count} <br />
        <button onClick={this.handleInc}>+</button>
        <button onClick={this.handleDsc}>-</button>
      </div>
    )
  }

  handleInc = () => {
    this.props.store.increment()
  }

  handleDsc = () => {
    this.props.store.decrement()
  }
}

const rootElement = document.getElementById('root')
ReactDOM.render(
  <React.StrictMode>
    <Counter store={appState} />
  </React.StrictMode>,
  rootElement,
)

import {observable, computed} from 'mobx'
import React from 'react'
import ReactDOM from 'react-dom'
import {observer} from 'mobx-react'

const t = new (class Temperature {
  // 온도 단위와 온도를 추적
  @observable unit = 'C'
  @observable temperatureCelsius = 25

  @computed get temperatureKelvin() {
    console.log('calculating Kelvin')
    return this.temperatureCelsius * (9 / 5) + 32
  }

  @computed get temperatureFahrenheit() {
    console.log('calculating Fahrenheit')
    return this.temperatureCelsius + 273.15
  }

  // observable의 값이 바뀔 때마다, 자동으로 변경된 값을 리턴 (엑셀 처럼!)
  @computed get temperature() {
    console.log('calculating temperature')
    switch (this.unit) {
      case 'K':
        return this.temperatureKelvin + 'K'
      case 'F':
        return this.temperatureFahrenheit + 'F'
      case 'C':
        return this.temperatureCelsius + 'C'
      default:
        throw new Error('Unexpected unit.')
    }
  }
})()

const App = observer(({temperature}) => (
  <div>
    {temperature.temperature} <br />
    <button onClick={() => (temperature.unit = 'F')}>F</button>
    <button onClick={() => (temperature.unit = 'K')}>K</button>
    <button onClick={() => (temperature.unit = 'C')}>C</button>
  </div>
))

ReactDOM.render(<App temperature={t} />, document.getElementById('root'))

import {observable} from 'mobx'
import React from 'react'
import ReactDOM from 'react-dom'
import {observer} from 'mobx-react'

const t = observable({
  unit: 'C',
  temperatureCelsius: 25,
  temperatureKelvin: function () {
    console.log('calculating Kelvin')
    return this.temperatureCelsius * (9 / 5) + 32
  },
  temperatureFahrenheit: function () {
    console.log('calculating Fahrenheit')
    return this.temperatureCelsius + 273.15
  },
  temperature: function () {
    console.log('calculating temperature')
    switch (this.unit) {
      case 'K':
        return this.temperatureKelvin() + 'K'
      case 'F':
        return this.temperatureFahrenheit() + 'F'
      case 'C':
        return this.temperatureCelsius + 'C'
      default:
        throw new Error('Unexpected unit.')
    }
  },
})

const App = observer(({temperature}) => (
  <div>
    {temperature.temperature()} <br />
    <button onClick={() => (temperature.unit = 'F')}>F</button>
    <button onClick={() => (temperature.unit = 'K')}>K</button>
    <button onClick={() => (temperature.unit = 'C')}>C</button>
  </div>
))

ReactDOM.render(<App temperature={t} />, document.getElementById('root'))

import { observable, computed, action, asMap } from "mobx";
import React from "react";
import ReactDOM from "react-dom";
import { observer } from "mobx-react";

class Temperature {
  id = Math.random();
  // 온도 단위와 온도를 추적
  @observable unit = "C";
  @observable temperatureCelsius = 25;

  @computed get temperatureKelvin() {
    console.log("calculating Kelvin");
    return this.temperatureCelsius * (9 / 5) + 32;
  }

  @computed get temperatureFahrenheit() {
    console.log("calculating Fahrenheit");
    return this.temperatureCelsius + 273.15;
  }

  // observable의 값이 바뀔 때마다, 자동으로 변경된 값을 리턴 (엑셀 처럼!)
  @computed get temperature() {
    console.log("calculating temperature");
    switch (this.unit) {
      case "K":
        return this.temperatureKelvin + "K";
      case "F":
        return this.temperatureFahrenheit + "F";
      case "C":
        return this.temperatureCelsius + "C";
      default:
        throw new Error("Unexpected unit.");
    }
  }

  // action을 정의할 수 있다.
  @action
  setUnit(newUnit) {
    this.unit = newUnit;
  }

  @action
  setCelsius(degrees) {
    this.temperatureCelsius = degrees;
  }

  @action("update temperature and unit")
  setTemperatureAndUnit(degrees, unit) {
    this.setCelsius(degrees);
    this.setUnit(unit);
  }
}

// 일반적인 array도 가능하다.
// const temps = observable([]);
// temps.push(new Temperature());
// temps.push(new Temperature());
// temps.push(new Temperature());

// array 선언
const temps = observable.map({
  Amsterdam: new Temperature(),
  Rome: new Temperature(),
  Seoul: new Temperature()
});

console.log(temps.entries());

const App = observer(({ temperatures }) => (
  <div>
   {* 진짜 javascript array와는 다르기 때문에 처리에 유의해야 한다. *}
   {* 참고: https://mobx.js.org/refguide/map.html *}
    {[...temperatures.entries()].map(([city, t]) => (
      <div key={t.id}>
        <div>
          ({city}) =&gt; {t.temperature}
        </div>
        <button onClick={() => t.setUnit("F")}>F</button>
        <button onClick={() => t.setUnit("K")}>K</button>
        <button onClick={() => t.setUnit("C")}>C</button>
      </div>
    ))}
  </div>
));

ReactDOM.render(<App temperatures={temps} />, document.getElementById("root"));