[英]How to refer a funtion as a template variable in Ionic Angular app?
我有一個Order
object 和一個客戶 Object。 Order
object 的JSON payload
如下所示:
{
"order_number" : 1,
"customer_id": 1
}
這是Customer
object 的JSON payload
{
"customer_id": 1,
"customer_name" : 1,
}
我有訂單頁面,我想在其中顯示訂單列表。 但不是order.customer_id
而是顯示customer_name
對於我有getCustomerById
,它將customer_id
作為參數並返回customer_name
。
這是我的OrdersPage
class:
import { Component, OnInit } from '@angular/core';
import { OrderService } from '../../services/order.service';
import { Order } from '../../models/order.model';
import { NavController, LoadingController } from '@ionic/angular';
import { Router } from '@angular/router';
import { Subscription } from 'rxjs';
import { CustomerService } from 'src/app/services/customer.service';
import { Customer } from 'src/app/models/customer.model';
@Component({
selector: 'app-orders',
templateUrl: './orders.page.html',
styleUrls: ['./orders.page.scss'],
})
export class OrdersPage implements OnInit {
sender;
customerName: string;
destinationName: string;
// viewOrders = false;
error;
orders: Order[];
subscription: Subscription;
constructor(private orderService: OrderService,
private navCtrl: NavController,
private router: Router,
private customerService: CustomerService
) { }
ngOnInit() {
this.orderService.refreshNeeded
.subscribe(() => {
this.getAllOrders();
});
this.getAllOrders();
}
getAllOrders() {
this.orderService.getAllOrders().subscribe(
(res: Order[]) => {
this.orders = res;
},
(error) => {
this.error = error;
});
}
getCustomerById(customerId: number): string {
this.customerService.getCustomerById(customerId).subscribe(
(customer: Customer) => {
this.customerName = customer.name;
}
);
return this.customerName;
}
}
這是orders.page.html
<ion-header>
<ion-toolbar color="dark">
<ion-button slot="end">
<ion-menu-button> </ion-menu-button>
</ion-button>
<ion-title>Orders</ion-title>
</ion-toolbar>
</ion-header>
<ion-content>
<ion-row>
<ion-col size-md="8" offset-md="2">
<ion-row class="header-row ion-text-center">
<ion-col>
Order number
</ion-col>
<ion-col>
Customer
</ion-col>
</ion-row>
<ion-row *ngFor="let order of orders; let i = index" class="data-row ion-text-center">
<ion-col>
{{order.order_number}}
</ion-col>
<ion-col>
{{order.customer_id}}
</ion-col>
<!-- <ion-col>
{{getCustomerById(order?.customer_id)}}
</ion-col> -->
</ion-row>
</ion-col>
</ion-row>
</ion-content>
這個 html 有效,但它返回order.customer_id
而不是customer_name
我試圖通過以這種方式調用模板中的函數來獲取名稱{{getCustomerById(order?.customer_id)}}
不起作用並且控制台中沒有錯誤以及。
在訂單列表中獲取customer_name
字段的最佳方法是什么?
這是我的customer.service.ts
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, Subject } from 'rxjs';
import { Customer } from '../models/customer.model';
import { catchError, tap } from 'rxjs/operators';
@Injectable({
providedIn: 'root'
})
export class CustomerService {
url = 'http://api.mydomain.com';
constructor( ) { }
getAllCustomers(): Observable<Customer[]> {
return this.httpClient.get<Customer[]>(`${this.url}/customers`).pipe();
}
getCustomerById(id: number): Observable<Customer> {
return this.httpClient.get<Customer>(`${this.url}/customer/${id}`).pipe();
}
}
正如@Muhammad Umair 所提到的,為每個客戶名稱向服務器發出請求並不是一個好的設計。 最好是發出一個請求來獲取所有想要的客戶名稱。 下面的解決方案沒有考慮到這一點。
這里最好使用 pipe。
“pipe 將數據作為輸入並將其轉換為所需的 output。” Angular 文檔
請注意,您獲取 curstomer 名稱的請求是異步的(這就是為什么模板中沒有顯示任何內容),在這里您還需要使用異步 pipe :
<ion-col>
{{ order.customer_id | getCustomerName | async }}
</ion-col>
這是 pipe (您應該將其插入組件模塊的聲明中。
import { Pipe } from '@angular/core';
@Pipe({
name: 'getCustomerName'
})
export class CustomerNamePipe {
constructor(private customerService: CustomerService) { }
transform(userIds, args) {
return this.customerService.getCustomerById(curstomerId);
}
}
同樣不是一個很好的解決方案,但鑒於您無法更改 API 中的任何內容的情況。 您可以將文件修改為此。
import { Component, OnInit } from '@angular/core';
import { OrderService } from '../../services/order.service';
import { Order } from '../../models/order.model';
import { NavController, LoadingController } from '@ionic/angular';
import { Router } from '@angular/router';
import { Subscription } from 'rxjs';
import { CustomerService } from 'src/app/services/customer.service';
import { Customer } from 'src/app/models/customer.model';
@Component({
selector: 'app-orders',
templateUrl: './orders.page.html',
styleUrls: ['./orders.page.scss'],
})
export class OrdersPage implements OnInit {
sender;
customerName: string;
destinationName: string;
// viewOrders = false;
error;
orders: Order[];
subscription: Subscription;
constructor(private orderService: OrderService,
private navCtrl: NavController,
private router: Router,
private customerService: CustomerService
) { }
ngOnInit() {
this.orderService.refreshNeeded
.subscribe(() => {
this.getAllOrders();
this.getAllCustomers();
});
this.getAllOrders();
this.getAllCustomers();
}
getAllOrders() {
this.orderService.getAllOrders().subscribe(
(res: Order[]) => {
this.orders = res;
},
(error) => {
this.error = error;
});
}
getAllCustomers() {
this.customerService.getAllCustomers().subscribe(
(customers: Customer[]) => {
this.customers = customers;
}
(error) => {
this.error = error;
});
}
getCustomerById(customerId: number): string {
const customer = this.customers.filter(customer => customer.customer_id === customerId );
return customer.customer_name;
}
}
正如@Noelmout 提到的那樣,使用 pipe 我只需稍作改動即可獲得customer_name
。
這是CustomerNamePipe
import { Pipe, PipeTransform } from '@angular/core';
import { CustomerService } from '../services/customer.service';
import { Customer } from '../models/customer.model';
import { pluck } from 'rxjs/operators';
@Pipe({
name: 'getCustomerName'
})
export class CustomerNamePipe implements PipeTransform {
customer: Customer;
constructor(private customerService: CustomerService) { }
transform(curstomerId, args) {
return this.customerService.getCustomerById(curstomerId).pipe(pluck('customer_name'));
}
}
這是訂單.page.html
<ion-col>
{{ order.customer_id | getCustomerName | async }}
</ion-col>
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