1.使用mobx里的computed無(wú)法生效class ODOM {  constructor(props) {    console.log('how many times')  }  @observable speed = 0  @action change(obj) {    console.log(obj)    Object.keys(obj).forEach(item => {      this[item] = obj[item]    })  }  @computed get velocity() {    console.log('entry')    return this.speed*60*60/1000  }}const model = new ODOM()let total = 0setInterval(() => {  model.change({    speed: ++total  })}, 3000)export default model2.computed里的console只被觸發(fā)了一次3.沒(méi)看出來(lái)代碼哪里的問(wèn)題，求解