Question

因此，我正在按照本课程使用angularfire2的先前版本（4.0），并且正在使用最新版本（5.0），并且我的代码遇到了这个问题。

我收到一个错误，指出 类型'AngularFireAction> []'无法分配给类型'Product []'。

export class AdminProductsComponent implements OnInit, OnDestroy {
products: Product[];
filteredProducts: any[];
subscription: Subscription;
tableResource: DataTableResource<Product>;
items: Product[];
itemCount: number;

constructor(private productService: ProductService) {
 this.subscription = this.productService.getAll().subscribe(products => {
  this.filteredProducts = this.products = products;
  this.initializeTable(products);
 });

}

private initializeTable(products: Product[]){
 this.tableResource = new DataTableResource(products);
  this.tableResource.query({ offset: 0})
    .then(items => this.items = items);
  this.tableResource.count()
    .then(count => this.itemCount = count);
}

reloadItems(params){ 
 if(!this.tableResource) return;
 this.tableResource.query(params)
    .then(items => this.items = items);
}

filter(query: string){
   this.filteredProducts = (query) ?
   this.products.filter(p => 
   p.title.toLowerCase().includes(query.toLowerCase())) :
   this.products; 
}

ngOnDestroy(){
  this.subscription.unsubscribe();
}


}

这是产品服务代码

export class ProductService {

constructor(private db: AngularFireDatabase) { }

create(product){
  return this.db.list('/products').push(product);
}

getAll(){
  return this.db.list('/products').snapshotChanges(); 
}

get(productId){
  return this.db.object('/products/' + productId);
}

update(productId, product){
  return this.db.object('/products/' + productId).update(product);
}

delete(productId){
  return this.db.object('/products/' + productId).remove(); 
}

}

Answer 1

您服务中的getAll()方法将返回snapshotChanges()。这是Observable<AngularFireAction<DatabaseSnapshot<{}>>[]>，而您正尝试将其传递给initializeTable(products: Product[])。这就是错误的意思。

要解决此问题，您需要像这样将.snapshotChanges()映射到Product[]：

getAll(): Observable<Product[]> {
    return this.db.list<Product>('/products')
        .snapshotChanges()
        .pipe(
            map(changes =>
                changes.map(c => {
                    const data = c.payload.val() as Product;
                    const id = c.payload.key;
                    return { id, ...data };
                })
            )
        );
}

Answer 2

GetAllProducts() : Observable<Product[]>{  returnthis.db.list('/products').snapshotChanges().pipe(
    map(changes => 
      changes.map(c => ({ key: c.payload.key, ...c.payload.val() as Product }))
    )
  );
  }

首先，您应该像上面一样添加GetAll()，然后您应该在函数中添加as Product接口。

类型“ AngularFireAction <数据库快照> {{} >> []”不可分配给类型“产品[]”

2 个答案: