“(string | undefined)[]”类型的参数不可分配给 'string[]' 类型的参数

Question

我有一些代码但是 angular 13 string[]

出错

'(string | undefined)[]' 类型的参数不可分配给 'string[]'.

类型的参数

在我的产品列表组件中

        ngOnInit(): void {
            this._getPro();
            this._getCate();
        }
        private _getPro(categoriesFilter?: string[]) {
            this.proService.getProducts(categoriesFilter).subscribe((pros) => {
                this.products = pros;
            });
        }
        private _getCate() {
            this.catService.getCategories().subscribe((cate) => {
                this.categories = cate;
            });
        }
        categoryFilter() {
            const selectedCategories = this.categories
                .filter((cate) => cate.checked)
                .map((cate) => cate.id);
            this._getPro(selectedCategories);
        }
    }

在我的产品服务中

//get all


     getProducts(categoriesFilter?: string[]): Observable<Product[]> {
            let params = new HttpParams();
            if (categoriesFilter) {
                params = params.append('categories', categoriesFilter.join(','));
            }
            return this.http.get<Product[]>(this.apiURLProducts, { params: params });
        }

this error here

Answer 1

你可以再添加一个过滤条件，保证每个分类都设置了id 属性，过滤函数为type guard predicate function:

TS Playground

categoryFilter() {
  const selectedCategories = this.categories
      .filter((c): c is typeof c & {
        checked: true;
        id: string;
      } => Boolean(c.checked && c.id))
      .map(({id}) => id);
  this._getPro(selectedCategories);
}

“(string | undefined)[]”类型的参数不可分配给 'string[]' 类型的参数

Argument of type '(string | undefined)[]' is not assignable to parameter of type 'string[]'

angular

typescript

string

observable

angular13