Typescript Error Type 'ArrayBuffer' is not assignable to type 'Item[]'

Question

In my ionic project, I want to get the rows from a table of a postgreSql data base, then assign the rows to a item[]: currentItems.

I check the return rows from postgreSql, it is in format as:

[
 anonymous 
 {
   name: jack,
   email: [email protected]
 }
 anonymous 
 {
   name: mark,
   email: [email protected]
 }
]

however, when I assign it to item[]: currentItems, I get the error as: Typescript Error Type 'ArrayBuffer' is not assignable to type 'Item[]'.

Below are part of my inoic code:

item.ts:

export class Item {

  constructor(fields: any) {
    // Quick and dirty extend/assign fields to this model
    for (const f in fields) {
      // @ts-ignore
      this[f] = fields[f];
    }
  }

}

list-master.ts:

export class ListMasterPage {
  currentItems: Item[];

  params: { uid: string } = {
    uid: "test"
  };

  constructor(public navCtrl: NavController,
    public items: Items,
    public modalCtrl: ModalController,
    public globalvar: GlobalvarProvider,
    public toastCtrl: ToastController) {

    this.params.uid = this.globalvar.userIdentifier
    this.items.query(this.params).subscribe((resp) => {
    /* here assign the received rows from database to the currentItems */
      this.currentItems = resp;
    }, (err) => {
    });;
  }

items.ts

export class Items {

  constructor(public api: Api) { }

  query(params?: any) {
    /* here get the rows from the postgresql database, I have confirmed the data received is in the format mentioned in above question description */
    return this.api.get('getfriends', params);
  }

  add(item: Item) {
  }

  delete(item: Item) {
  }

}

Thanks

To confirm, if you console.log(resp), what exactly do you see? The response probably needs some kind of manual conversion to an Item[]. — Matt McCutchen
– Matt McCutchen, Commented Aug 25, 2018 at 15:15
@MattMcCutchen, thanks Matt. it show: resp is: [object Object],[object Object] — lei lei
– lei lei, Commented Aug 26, 2018 at 1:13

Matt McCutchen · Accepted Answer · 2018-08-26 20:06:26Z

1

It looks like you probably have valid plain objects from parsing JSON. To troubleshoot why TypeScript thinks the type is ArrayBuffer, I'd need to see the declaration of the get method that is called in the Items.prototype.query method. If you want Item objects instead of plain objects, you'll have to instantiate them yourself, e.g.:

this.currentItems = (<any[]>resp).map((i) => new Item(i));

or use a serialization library.

answered Aug 26, 2018 at 20:06

Matt McCutchen

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