?用computed:

loadTopResult () {
    if (this.city && this.country) {
       let res = this.loadTop()
       return res
    }
}

watch和computed的區(qū)別

不能同時(shí)監(jiān)聽(tīng)兩個(gè)值，
不過(guò)你可以

data () {
    return {
        city: '',
        oldCity: '',
        country: '',
        oldCountry: ''
    }
}
watch:{
      city(cur,old){
            if (this.country !== this.oldCountry) {
                this.loadTop();
                this.oldCountry = this.country
            }
      },
      country(cur,old){
            if (this.city !== this.oldCity) {
                this.loadTop();
                this.oldCity = this.city
            }
      },
    }

可以做個(gè)計(jì)數(shù)器
國(guó)家改變: count++;
城市改變: count++;

watch: {
    count(value){
       if(2 === value) {
            // 觸發(fā)code
            
           this.count = 0;
       }
   }
}

拋磚引玉啊, 方法比較拙, 對(duì)每個(gè)改變的執(zhí)行此處的判斷并沒(méi)有寫(xiě), 如果覺(jué)得方法可行再補(bǔ)上

不過(guò)如果是聯(lián)動(dòng)的話, 國(guó)家變了, 城市自然為空, 所以你說(shuō)的邏輯好像不成立, 我只是猜測(cè).

用computed定義一個(gè)address對(duì)象吧，然后再去watch addres

data() {
  return {
    city: '',
    country: ''
  }
},
computed: {
  address() {
    const { city, country } = this
    return {
      city,
      country
    }
  }
},
watch: {
  address: {
    handler: function(val) {
      console.log('address change: ', val)
    },
    deep: true
  }
}

只的在computed里面調(diào)用也行，不過(guò)要使用$nextTick，不然值會(huì)是更新前的值。

data() {
  return {
    city: '',
    country: ''
  }
},
computed: {
  address() {
    const { city, country } = this
    this.$nextTick(() => {
      console.log(this.city, this.country, 3333)
    })
    return {
      city,
      country
    }
  }
},