我正在尝试从本地服务器获取数据,但没有任何结果。这个想法是它由一个服务检索,该服务传回一个observable,并且需要数据的任何组件都订阅了observable。
dish.service.ts
import {Dish} from '../shared/dish';
import {DISHES } from '../shared/dishes';
import {Observable, of} from 'rxjs';
import { delay } from 'rxjs/operators';
import { map } from 'rxjs/operators';
import { HttpClient } from '@angular/common/http';
import { baseURL } from '../shared/baseurl';
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root'
})
export class DishService {
constructor(private http: HttpClient) {
}
getDishes(): Observable<Dish[]>{
console.log("Hey");
return this.http.get<Dish[]>(baseURL + 'dishes');
}
}
menu.component.ts
import { Component, OnInit, Inject } from '@angular/core';
import { Dish } from '../shared/dish';
import {DishService} from '../services/dish.service';
@Component({
selector: 'app-menu',
templateUrl: './menu.component.html',
styleUrls: ['./menu.component.scss']
})
export class MenuComponent implements OnInit {
dishes: Dish[];
constructor(private dishService: DishService, @Inject('BaseURL') private BaseURL) { }
ngOnInit() {
(dishService => dishService.getDishes().subscribe(dishes => this.dishes = dishes))
}
}
它将数据传递给menu.component.html,在添加服务器之前工作正常,所以我知道不是这样。这是有趣的:第一个代码示例中的console.log(“Hey”)不会执行。这就像是MenuSeriv甚至没有调用dishSerivce.getDishes()方法。我不知道如何深入挖掘。有没有人有任何其他想法?
它应该如下,
ngOnInit() {
dishService.getDishes().subscribe(dishes => this.dishes = dishes))
}
问题是符合的
(dishService => dishService.getDishes().subscribe(dishes => this.dishes = dishes))
基本上你在这里声明一个函数,而不是调用它。你的代码相当于
ngOnInit(){
function(dishService){
return dishService.getDishes().subscribe(dishes => this.dishes = dishes);
}
}
考虑以下代码实际调用函数,将this.dishService
作为参数传递。
(dishService => dishService.getDishes().subscribe(dishes => this.dishes = dishes))(this.dishService)
话虽如此,正确的方法是
ngOnInit() {
this.dishService.getDishes()
.subscribe(dishes => this.dishes = dishes);
}