Vue.js Vue 2 如何在全局函数中返回观察者

Hello I have this problem:in main.js I have a global function getSites, needed to retrive a list of sites from API.
This function work with async/await and returns data sites asynchronously.
I also have a global variable called lockSitesLoading which i set to true when i start to fetch data from API, I need this to prevent client to make a new request to server.
In the first function getSites I need to check this variable lockSitesLoading and, if it's true, start to watch it till it becomes false. At this point I want to call getSites recursively.
The problem starts now, because when i start watch the variable this function doesn't wait for the variable to become false, but returns undefined.
Here there is my code:

Compartant.vue:(用谷歌翻译翻译)

  async mounted() {
    let vm = this;
    const sites = await vm.getSites();
    vm.sites = sites.data
  },

Main.js:

 async getSites() {
      let vm = this;
      if (vm.$store.state.lockSitesLoading) {
        vm.$watch('$store.state.lockSitesLoading', () => vm.getSites());
      } else {
        return vm._getSitesOnline();
        //this is the function that effectively get datas from server
      }

我试着用这种方法解决它，但行不通.有什么好主意吗？