TypeScript 类型比较 Type 'Site | Site[]' 不可分配到类型 'Site'

Question

I have the following interfaces

export interface Site {
  id: number;
  path: string;
  siteLink: string;
  features: Feature[];
}

export interface SiteResponse {
  data: Site | Site[];
  meta?: any;
}

That's being used because I may retrieve an object or an array of objects. Depends on API route I call.

And here is my service's method I try work with

getSiteById(id: number): Observable<SiteResponse> {
    return this.http.get<SiteResponse>(this.API_URL + '/' + id);
  }

And it's subscription

this.ss.getSiteById(this.id).subscribe((x: SiteResponse) => {
        const site: Site = x.data;

        this.link.setValue(site.siteLink);
        this.imagePreview = site.path;
        site.features.forEach(feature => {
          this.features.push(this.fb.control(feature, Validators.required));
        });
        this.isPending = false;
      });

For me it looks OK, but not for the validator.

error TS2322: Type 'Site | Site[]' is not assignable to type 'Site'. Type 'Site[]' is not assignable to type 'Site'. Property 'id' is missing in type 'Site[]'.

Answer 1

通过添加额外的类型声明const site: Site = <Site>x.data;