Observer.ts

Observer.ts

// Comportamental - Como os objetos dependentes se mantem atualizados

interface Observer {
  update: () => void
}

interface Subject {
  attach: (observer: Observer) => void,
  detach: (observer: Observer) => void,
  notify: () => void,
}

interface WeatherStation extends Subject {
  updateTemperature: (value: number) => void
}


const WeatherStation = () : WeatherStation => {
  const state = {
    temperature: 0
  }

  let observers: Observer[] = []

  const attach = (observer: Observer) => observers.push(observer)
  const detach = (observer: Observer) => observers = observers.filter(o => o !== observer)
  const notify = () => observers.forEach(o => o.update())

  const updateTemperature = (value: number) => {
    state.temperature = value
    notify()
  }

  return {
    attach, 
    detach, 
    notify,
    updateTemperature
  }
}

const Cooler = (name: string): Observer => {
  const state = { name }

  const update = () => {
    console.log(`
      Atualização de temperatura detectada!
      Realizando checks de ventilação no ${state.name}...
    `)
  }

  return { update }
}

const weatherStation = WeatherStation()
const cooler1 = Cooler('Cooler 1')

weatherStation.attach(cooler1)

weatherStation.updateTemperature(10)
weatherStation.updateTemperature(5)

weatherStation.detach(cooler1)

weatherStation.updateTemperature(5)