路由器解析器不渲染组件

我有这个路由器解析器来从 Google Firestore 检索数据。我正在尝试使用解析器来提前获取数据。当我将调试器放置在解析函数中时，它会显示从服务器检索的数据。但它永远不会从resolve()方法返回。谁能帮我一下。

路由模块

const routes: Routes = [
    { path: '', component: HomeComponent},
    { path: 'projects', component: ProjectsComponent, resolve: {projectData: ProjectResolver} },
    { path: 'about', component: AboutComponent}
];

应用模块

  providers: [
    ProjectService,
    ProjectResolver
  ],

解析器服务

import { Observable } from 'rxjs';
import { ActivatedRouteSnapshot, RouterStateSnapshot, Resolve } from '@angular/router';
import { Injectable } from '@angular/core';
import { ProjectService } from './project.service';
import { map } from "rxjs/operators";
import { Project } from './project.model';

@Injectable()
export class ProjectResolver implements Resolve<Project[]> {

    constructor(private projectService: ProjectService ) {

    }

    resolve(route: ActivatedRouteSnapshot, router: RouterStateSnapshot) : Observable<Project[]> | any{
        return this.projectService.getProjects().pipe(map(project => {
            return project //Debugger shows fetched data(Array of projects)
        }
        ));
    }
}

项目服务

import { AngularFirestore } from 'angularfire2/firestore';
import { Observable } from "rxjs";
import { Injectable } from "@angular/core";

@Injectable()
export class ProjectService {

    constructor(private db: AngularFirestore) {}

    getProjects(): Observable<any> {
        return this.db.collection('currentProjects').valueChanges();
    }

}

** 项目组件（该组件从未被解析器加载 )**

import { Component, OnInit, Injectable } from '@angular/core';
import { Project } from './project.model';
import { ActivatedRoute } from '@angular/router';
import { ProjectService } from './project.service';
import { Observable } from 'rxjs';

@Component({
  selector: 'app-projects',
  templateUrl: './projects.component.html',
  styleUrls: ['./projects.component.css']
})

export class ProjectsComponent implements OnInit {

   projects: Project[] = [];

  constructor(private route: ActivatedRoute, private projectService: ProjectService) { 
  }

  ngOnInit() {
      this.route.data.subscribe((data: Project[]) => {
        this.projects = data['projectData'];
      })
  }

}

问题是 Angular Firebase Observable（事件流）永远不会像正常的“observable”一样完成，因此它永远不会解析。我使用“take”运算符修改了 Observable 以获取第一项并强制完成。

this.db.collection('currentProjects').valueChanges().take(1);

Changes:

• 删除了项目服务
• 修改后的ProjectResolver
• 修改后的项目组件

我在下面发布了我的问题的解决方案：

项目解析器（工作中）

export class ProjectResolver implements Resolve<any> {

    constructor(private db: AngularFirestore) {

    }

    resolve(route: ActivatedRouteSnapshot, router: RouterStateSnapshot) : any{

        return Observable.from(this.db.collection('currentProjects').valueChanges()
            .do(data => {  
                return data
            }).take(1))
    }
}

项目组件（工作）

export class ProjectsComponent implements OnInit {

  private projects: Project[];

  constructor(private route: ActivatedRoute) {

  }

  ngOnInit() {
    this.route.data.subscribe((data) => {
      this.projects = data['projectData'];
    })
  }
}