CODEWITHSUNDEEP
typescriptionic4
geeth chowdary
geeth chowdary

Reputation: 25

Issue with Sequential function calls using async await

I found that when I tried to call functions initializeItems() need to be called first. but checkList() is getting called before initializeItems()

  initializeItems() {

    this.dataService.readLocalData().subscribe( data => {
      console.log('Local Data');
      this.items = data;
      // console.log(this.items);
      this.tempItems = [];
      for (const i of this.items.material ){
        console.log(i['material-name']);
        this.tempItems.push( i['material-name'] );
      }
      console.log('***********************************************');
      console.log(this.tempItems);
    });
  }

  checkList(ev: any){
    // set val to the value of the searchbar
    const val = ev.target.value;
    console.log(val);
    console.log(this.tempItems);
    // if the value is an empty string don't filter the items
    if (val && val.trim() !== '') {
      this.tempItems = this.tempItems.filter((item) => {
        return (item.toLowerCase().indexOf(val.toLowerCase()) > -1);
      });
    }
  }

  async getItems(ev: any) {
    // Reset items back to all of the items
    await this.initializeItems(); //This need to execute first
    await this.checkList(ev); //But this getting executed
  }

If the function calls sequentially. My result will be

initializeItems()

variable tempItems will be//full list

then

checkList()

variable tempItems will be //filtered list from a searchable drop-down

Upvotes: 0

Views: 34

Answers (1)

Nicholas Tower
Nicholas Tower

Reputation: 84902

await is meant for use with promises. Since initializeItems doesn't return a promise, await doesn't actually wait for anything. You need to modify initializeItems to return a promise. My guess is that you expect the subscribe callback to be invoked exactly once, and at that point the promise should resolve, so you'd want to do this:

initializeItems() {
  return new Promise((resolve) => { // <---- creating a promise
    this.dataService.readLocalData().subscribe( data => {
      console.log('Local Data');
      this.items = data;
      // console.log(this.items);
      this.tempItems = [];
      for (const i of this.items.material ){
        console.log(i['material-name']);
        this.tempItems.push( i['material-name'] );
      }
      console.log('***********************************************');
      console.log(this.tempItems);
      resolve(); // <-- resolving the promise
    });
  }
}

Upvotes: 1

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