我想打印产品的历史记录。我在ActivatedRoute.params中有一个产品ID。在ngOnInit方法中,我必须获取产品的所有历史记录并将其分配给变量。然后,我想将产品映射到productHistory,因为我想要带历史记录的最后一个版本。但问题在于获得历史。获取历史记录的方法返回Promise和我无法获得产品历史的长度,当我使用此属性,我得到未定义。从服务中加载后怎样才能得到这个属性?Angular - 从Promise同步
我想执行getHistory()后执行方法。
我的代码:
ProductService.ts:
import { Injectable } from '@angular/core';
import { Headers, Http } from '@angular/http';
import 'rxjs/add/operator/toPromise';
// rest imports
@Injectable()
export class ProductService {
// URL to web api
private projectsUrl = 'http://localhost:8080/products';
private headers = new Headers({'Content-Type': 'application/json'});
constructor(private http: Http) {}
getHistory(id: number): Promise<ProductHistory[]> {
const url = `${this.projectsUrl}/projectId/${id}`;
return this.http.get(url)
.toPromise()
.then(response => response.json() as ProductHistory[])
.catch(this.handleError);
}
handleError() {
//...
// implementation is irrelevant
}
}
ProductHistoryComponent.ts:
import { Component, Input, OnInit } from '@angular/core';
import { ActivatedRoute, Params } from '@angular/router';
import { Location } from '@angular/common';
import { ProductService } from './product.service';
import { ProductHistory } from './product-history';
import { Product } from './model/product';
import 'rxjs/add/operator/switchMap';
@Component({
selector: 'product-history',
templateUrl: './product-history.component.html',
styleUrls: [ './product-history.component.css' ]
})
export class ProductHistoryComponent implements OnInit {
auditProducts: ProductHistory[] = new Array<ProductHistory[]>();
selectedProduct: ProductHistory;
constructor(
private route: ActivatedRoute,
private location: Location,
private productService: ProductService
) {}
ngOnInit(): void {
let id: number = this.route.snapshot.params['id'];
this.productService.getHistory(id)
.then(history => this.historyProducts = history);
this.productService.getProduct(id)
.then(product => {
let lastVersion: ProductHistory = this.createLastVersion(product);
this.auditProducts.push(lastVersion);
});
}
onSelect(ProductHistory: ProductHistory): void {
this.selectedProduct = ProductHistory;
this.compare(this.selectedProduct);
}
goBack(): void {
this.location.back();
}
compare(history: ProductHistory): void {
let previous: ProductHistory;
if (history.changeNumber != null && history.changeNumber > 1) {
previous = this.historyProducts[history.changeNumber - 2];
if (typeof previous != 'undefined') {
this.setPreviousDiffsFalse(previous);
if (previous.name !== history.name) {
history.nameDiff = true;
}
if (previous.price !== history.price) {
history.priceDiff = true;
}
}
}
}
createLastVersion(product: Product): ProductHistory {
let lastVersionProduct: ProductHistory = new ProductHistory();
lastVersionProduct.id = this.historyProducts.length + 1;
lastVersionProduct.name = product.name;
lastVersionProduct.price = product.price;
lastVersionProduct.changeNumber = this.historyProducts[this.historyProducts.length - 1].changeNumber + 1;
return lastVersionProduct;
}
setPreviousDiffsFalse(previous: ProductHistory): void {
previous.nameDiff = false;
previous.priceDiff = false;
}
}
无法从承诺中获得同步的价值,而不是从橙子获得苹果。 –