我正在构建一个购物车,使用了一个购物车服务,通过将商品数量分配给产品/向购物车添加产品。除了使用 take 以获取可观察项的第一实例之外,是否还有其他方法?
我已经正确导入了 take 操作符,但它仍然给出运行时错误。如果我不使用 take,则分配的数量是某个随机整数而不是1。
在下面的代码中,当对可观察对象使用 take() 时,我遇到了以下错误:
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import { Product } from '../app/models/product';
import 'rxjs/add/operator/take';//tried this one too
import { take } from 'rxjs-compat/operator/take';
@Injectable({
providedIn: 'root'
})
export class ShoppingCartService {
constructor(private db: AngularFireDatabase) { }
private create() {
return this.db.list('/shopping-carts').push({
dateCreated: new Date().getTime()
});
}
private getCart(cartId: string) {
return this.db.object('/shopping-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;
}
async addToCart(product: Product) {
let cartId = await this.getOrCreateCartId();
let item$ = this.db.object('/shopping-carts/'+cartId+'/items/'+product.$key);
item$.take(1).subscribe(item=>{
if(item.$exists()) item$.update({quantity : item.quantity + 1});
else item$.set({product : product , quantity : 1 });
});
}
}
Error: Uncaught (in promise): TypeError: item$.take is not a function. (In 'item$.take(1)', 'item$.take' is undefined) http://localhost:4200/main.js:1581:35 step@http://localhost:4200/main.js:1534:27 fulfilled@http://localhost:4200/main.js:1506:62 onInvoke@http://localhost:4200/vendor.js:46707:39 run@http://localhost:4200/polyfills.js:2483:49 http://localhost:4200/polyfills.js:3217:37 onInvokeTask@http://localhost:4200/vendor.js:46698:43 runTask@http://localhost:4200/polyfills.js:2533:57 drainMicroTaskQueue@http://localhost:4200/polyfills.js:2940:42 invokeTask@http://localhost:4200/polyfills.js:2845:40 invokeTask@http://localhost:4200/polyfills.js:3885:20 globalZoneAwareCallback@http://localhost:4200/polyfills.js:3911:27
resolvePromise — zone.js:814
(anonymous function) — zone.js:724
fulfilled — products.component.ts:11
onInvoke — core.js:14143
run — zone.js:138
(anonymous function) — zone.js:872
onInvokeTask — core.js:14134
runTask — zone.js:188
drainMicroTaskQueue — zone.js:595
invokeTask — zone.js:500
invokeTask — zone.js:1540
globalZoneAwareCallback — zone.js:1566
take
删除所有其他的导入,只使用这一个,并确保如果你正在导入Observable
,它应该是import { Observable } from 'rxjs';
。 - dream88