[英]Property 'update' does not exist on type 'Observable<{}>'. Firebase 5 AngularFire2 5
我正在尝试在firebase中创建/更新购物车。 我正在使用具有将localStorage ID添加到firebase的功能的服务,如果产品已经存在,则添加购物车中的数量,否则创建新的数量。 控制台TypeError中发生错误:无法读取null的属性'quantity',并且在shopping-cart service.ts中编译时也出错:
购物,cart.service.ts
import { take } from 'rxjs/operators';
import { AngularFireDatabase, snapshotChanges } from 'angularfire2/database';
import { Injectable } from '@angular/core';
import { Product } from './models/product';
@Injectable({
providedIn: 'root'
})
export class ShoppingCartService {
constructor(private db: AngularFireDatabase) { }
private create(){
console.log('shoping service')
return this.db.list('/shopping-carts').push({
dateCreated: new Date().getTime()
});
}
private getCart(cartId: string){
return this.db.object('/shoping-carts/'+ cartId);
}
private async getOrCreateCartId(){
let cartId = localStorage.getItem('cartId');
if(cartId) return cartId;
let result = await this.create();
localStorage.setItem('cartId', result.key);
return result.key;
}
private getItem(cartId: string, productId: string){
return this.db.object('/shopping-carts/' + cartId + '/items/' + productId).valueChanges();
}
async addToCart(product: Product){
let cartId = await this.getOrCreateCartId();
let item$ = this.getItem(cartId, product.key);
item$.pipe(take(1)).subscribe( item => {
item$.update({ product: product, quantity: (item.quantity || 0) + 1});
});
}
shoppng-cart.service.ts(文件的相关部分)
private getItem(cartId: string, productId: string){
return this.db.object('/shopping-carts/' + cartId + '/items/' + productId).valueChanges();
}
async addToCart(product: Product){
let cartId = await this.getOrCreateCartId();
let item$ = this.getItem(cartId, product.key);
item$.pipe(take(1)).subscribe( item => {
item$.update({ product: product, quantity: (item.quantity || 0) + 1});
});
}
产品card.component.ts
import { ShoppingCartService } from './../shopping-cart.service';
import { Product } from './../models/product';
import { Component, OnInit, Input } from '@angular/core';
@Component({
selector: 'product-card',
templateUrl: './product-card.component.html',
styleUrls: ['./product-card.component.css']
})
export class ProductCardComponent implements OnInit {
@Input('product') product;
@Input('show-actions') showActions = true;
constructor(private cartService:ShoppingCartService) { }
addToCart(product:Product){
this.cartService.addToCart(product);
}
ngOnInit() {
}
}
产品card.component.html
<div *ngIf="product.title" class="card m-auto">
<img class="card-img-top" [src]="product.imageUrl" *ngIf="product.imageUrl" alt="{{ product.title }}">
<div class="card-body pb-0">
<h5 class="card-title">{{product.title}}</h5>
<p>{{product.price | currency: 'USD'}}</p>
</div>
<div class="card-footer p-0 border-top">
<button *ngIf="showActions" (click)="addToCart(product)" class="btn btn-primary btn-block">Add to Cart</button>
</div>
</div>
product.ts:
export interface Product{
key: string;
title: string;
price: number;
category: string;
imageUrl: string;
}
错误是非常具有描述性的observable没有这样的属性。 因为valueChanges()
函数返回一个observable,它只有数据。 但是AngularFireObject
具有更新功能,您需要使用它。 所以你需要修改你的代码,如:
private getItem(cartId: string, productId: string): {
return this.db.object<any>('/shopping-carts/' + cartId + '/items/' + productId);
}
async addToCart(product: Product){
let cartId = await this.getOrCreateCartId();
let item$ = this.getItem(cartId, product.key);
item$.valueChanges().pipe(take(1)).subscribe((item: any) => {
item$.update({ product: product, quantity: (item.quantity || 0) + 1});
});
}
经过大量的搜索和调试也是Yevgen的一部分回答我修改了我的代码以摆脱ERROR TypeError:无法读取属性'quantity'的null 。 如果我使用valueChanges
则会在添加新购物valueChanges
出错。 所以我改为snapshotChanges
并把它存在的一些逻辑,现在工作正常。 如果有人仍然更新我的答案,那么非常欢迎。
private getItem(cartId:string, productId:string) {
return this.db.object < any > ('/shopping-carts/' + cartId + '/items/' + productId);
}
async addToCart(product:Product) {
let cartId = await this.getOrCreateCartId();
let item$ = this.getItem(cartId, product.key);
item$.snapshotChanges().pipe(take(1)).subscribe((item:any) => {
if (item.key != null) {
item$.update( {quantity:( item.payload.val().quantity || 0) + 1});
}
else{
item$.set( {product:product, quantity:1});
}
});
}
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