angular - 如何在 Angular 4 或 7 中设置 Observable 属性？

Question

我正在尝试使用从轮播服务中的 json 文件中检索到的数据设置 slides[] 属性。我的 carousel 组件注入 carousel-service 并调用公共 getSlides() 函数，但返回值是一个空数组。

我究竟做错了什么？

附上代码：

//carousel.component.ts
import { Component, OnInit } from '@angular/core';
import { CarouselService } from '../../services/carousel.service';

@Component({
  selector: 'app-carousel',
  templateUrl: './carousel.component.html',
  styleUrls: ['./carousel.component.css']
})
export class CarouselComponent implements OnInit {

  slides: string[];

  constructor(private carouselService: CarouselService) { }

  ngOnInit() {
    this.getSlides();
  }

  getSlides(): void {
    this.carouselService.getSlides()
      .subscribe(slides => {
        console.log('show slides', slides);
        this.slides = slides
      });
  }

}

轮播服务.ts

import { Injectable } from '@angular/core';
import { Observable, of, ObservableInput } from 'rxjs';
import { HttpClient } from '@angular/common/http';
import { catchError, map, tap } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class CarouselService {

  slides: string[] = [];

  constructor(private http: HttpClient) {
    this.getJSON().subscribe(data => {
      this.slides = data['Carousel'];
      console.log('data loaded');
    });
  }

  public addSlide(title: string) {
    this.slides.push(title);
  }

  public getSlides(): Observable<string[]> {
    return of(this.slides);
  }

  private getJSON(): Observable<Object> {
    return this.http.get("./assets/carousel.json");
  }
}

标签： angulartypescriptserviceobservable

Answer 1

我在评论部分接受了 Suryan 的建议，并重构了我的代码以使用 async/await 函数，并且在前端，组件已更新为包含属性。

import { Injectable } from '@angular/core';
import { Observable, of, ObservableInput } from 'rxjs';
import { HttpClient } from '@angular/common/http';
import { catchError, map, tap } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class CarouselService {    

  constructor(private http: HttpClient) { }    

  async public getJSON(): Observable<Object> {
    return this.http.get("./assets/carousel.json");
  }
}

//carousel.component.ts
import { Component, OnInit } from '@angular/core';
import { CarouselService } from '../../services/carousel.service';

@Component({
  selector: 'app-carousel',
  templateUrl: './carousel.component.html',
  styleUrls: ['./carousel.component.css']
})
export class CarouselComponent implements OnInit {

  slides: string[];

  constructor(private carouselService: CarouselService) { }

  ngOnInit() {
    this.getSlides();
  }

  getSlides(): void {
    this.carouselService.getSlides()
      .subscribe(await slides => {
        console.log('show slides', slides);
        this.slides = slides
      }.bind(this));
  }

}

请注意，有更好的方法进行异步操作。我刚刚阅读了 Angular.io 文档，并且可以使用异步管道。