如何使用一个可观察的一个来更新另一个

Question

我正在尝试使用可观察的收藏夹$构建同一类型的其他数组时。我期望fairition $可观察到的可观察到的类型code> corversy的数组，并且我可以设置一个类变量，以便使用其内容更新。我正在在ngoninit（）中进行订阅。

在我的服务的函数中，我正在尝试迭代University对象的收到的列表，并设置属性iSfavureite值，如果它们的等效对象在<<<<代码>收藏夹$ 可观察的数组。

这是不起作用的，我不知道为什么...

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { University } from './university.model';
import { map } from 'rxjs/operators';
import { Store, Select } from '@ngxs/store';
import { FavouritesState } from './state';

@Injectable({
  providedIn: 'root'
})
export class UniversityService {
  @Select(FavouritesState.getFavourites) favourites$: Observable<University[]>;

  favs: University[] = [];

  constructor(private http: HttpClient) { }

  ngOnInit(): void {
    this.favourites$.subscribe(f => {
      console.log('favs updated');
      this.favs = f;
    });
  }

  public getUniversities = (country: string, name: string) : Observable<University[]> => this.http
    .get<University[]>(`http://universities.hipolabs.com/search?country=${country}&name=${name}`)
    .pipe(map(this.produceUniArr));

  private produceUniArr(respData: University[]) {
    const uniArr: University[] = [];
    respData.forEach(element => {
      const uni = new University(element['state-province'], element.country, element.name, element.web_pages, element.domains, element.alpha_two_code);

      const isContains = this.favs?.filter(u => u.country === element.country && u.name === element.name).length > 0;
      console.log(isContains);
      uni.isFavourite = isContains;

      uniArr.push(uni);
    });
    return uniArr;
  }
}

线console.log（iscontains）;始终在Dev Console中打印出false。

此行console.log（'Favs Updated'）;永远不会打印出来。我假设使用subscribe会导致favs变量被填充。我错误地使用了这个？

getuniversities（）函数是从搜索组件中调用的：

import { HttpClient } from '@angular/common/http';
import { Component, OnInit } from '@angular/core';
import { Select, Store } from '@ngxs/store';
import { Observable, Subscription } from 'rxjs';
import { FavouritesState } from '../shared/state';
import { University } from '../shared/university.model';
import { UniversityService } from '../shared/university.service';
import { Results } from '../shared/results.actions';
import { Search } from '../shared/search.actions';

@Component({
  selector: 'app-search',
  templateUrl: './search.component.html',
  styleUrls: ['./search.component.css']
})
export class SearchComponent implements OnInit {
  @Select(FavouritesState.getFavourites) favourites$: Observable<University[]>;
  @Select(FavouritesState.getSearchResults) searchResults$: Observable<University[]>;
  @Select(FavouritesState.getCountry) country$: Observable<string>;
  @Select(FavouritesState.getSchoolName) schoolName$: Observable<string>;

  favs: University[];
  country: string;
  schoolName: string;

  constructor(private http: HttpClient, private universityService: UniversityService, private store: Store) {
  }

  ngOnInit(): void {
    this.searchResults$.subscribe(res => {
      this.favs = res;
    });
    this.country$.subscribe(c => {
      this.country = c;
    });
    this.schoolName$.subscribe(n => {
      this.schoolName = n;
    });
  }

  doAutoPost(value) {
    console.log(value,this.isLoading , this.country , this.schoolName);
    if (!this.isLoading && this.country !== '' && this.schoolName !== '') {
      this.doPost( { country: this.country, name: this.schoolName } );
    }
    else{
      console.log('not searching');
    }
  }

  isLoading: boolean = false;
  loader: Subscription;

  doPost(postData: { country: string; name: string }): void {
    this.isLoading = true;

    if (this.loader) {
      this.loader.unsubscribe();
      console.log('unsubscribed');
    }

    console.log('loading...');

    this.loader = this.universityService
      .getUniversities(postData.country, postData.name)
      .subscribe(unis => {
        console.log('loaded.');
        this.store.dispatch(new Results.Found(unis));
        this.isLoading = false;
      });
  }
}

我如何使用fairter $ array正确填充了University>大学的数组从productuniarr函数返回的对象？另外，我是否使用收藏夹$可正确观察到？ this.favs应使用Universities的最爱列表进行更新。

（我当前的工作知识是， href =“ https://github.com/horacebury/favuni” rel =“ nofollow noreferrer”>在这里。

Answer 1

事实证明，该服务的构造函数和ngoninit没有被调用（我不知道为什么），所以我必须将所有@select

如果有人可以解释如何完成这项工作，我将选择该帖子作为答案。