[英]TypeError: Cannot read properties of null (reading '_rawValidators')
[英]TypeError: Cannot read properties of null (reading 'quantity')
購物車.service.ts
async addToCart(product:Product){
this.updateItem(product,1)
}
async removeFromCart(product:Product){
this.updateItem(product, -1)
}
private getItem(cartId: string, productId: string) {
return this.db.object('/shopping-carts/' + cartId + '/items/' + productId);
}
private async getOrCreateCartId():Promise<string>{
let cartId = localStorage.getItem('cartId')
if(cartId) return cartId;
let result = await this.create();
localStorage.setItem('cartId',result.key!);
return result.key!;
}
private async updateItem(product:Product,change:number){
let cartId = await this.getOrCreateCartId();
let item$ = this.getItem(cartId,product.key);
item$.valueChanges().take(1).subscribe((item:any)=>{
let quantity = (item.quantity || 0) + change; // error
if (quantity === 0) item$.remove();
else item$.update({
title:product.title,
imageUrl:product.imageUrl,
price: product.price,
quantity:quantity
})
})
}
錯誤:-
在控制台中收到此錯誤時,它會在數量為零時從購物車中刪除商品(購物車中已經存在的產品),但是當我嘗試將商品添加到購物車時,它不允許我將產品添加到購物車並在控制台中向我顯示此錯誤
ERROR TypeError: Cannot read properties of null (reading 'quantity')
at SafeSubscriber._next (shopping-cart.service.ts:61)
at SafeSubscriber.__tryOrUnsub (Subscriber.js:183)
at SafeSubscriber.next (Subscriber.js:122)
at Subscriber._next (Subscriber.js:72)
at Subscriber.next (Subscriber.js:49)
at TakeSubscriber._next (take.js:35)
at TakeSubscriber.next (Subscriber.js:49)
at MapSubscriber._next (map.js:35)
at MapSubscriber.next (Subscriber.js:49)
at Notification.observe (Notification.js:20)
我認為這是一個異步等待問題
let item$ = this.getItem(cartId,product.key);
所以 item 未定義,這就是為什么你有properties of **null**
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