Angular 6: Convert eager loading to lazy loading

Question

I have a complete angular app that uses eager loading. I want to convert it to lazy loading, but because I have guard on all of my routes and all of them are sub routes to one main route that is guarded, I don't know if it's possible to do it and still make it function like with eager loading.

This is my routing array in app-routing.module:

// Routing array - set routes to each html page
const appRoutes: Routes = [
  { path: 'login/:id', canActivate: [AuthGuard], children: [] },
  { path: '', canActivateChild: [AuthGuard], children: [
    { path: '', redirectTo: '/courses', pathMatch: 'full' },
    { path: 'courses', component: CourseListComponent,  pathMatch: 'full'},
    { path: 'courses/:courseId', component: CourseDetailComponent, pathMatch: 'full' },
    { path: 'courses/:courseId/unit/:unitId', component: CoursePlayComponent,
      children: [
        { path: '', component: CourseListComponent },
        { path: 'lesson/:lessonId', component: CourseLessonComponent, data:{ type: 'lesson'} },
        { path: 'quiz/:quizId', component: CourseQuizComponent, data: {type: 'quiz'} }
      ]}
    ]},
  { path: 'welcome', component: LandingPageComponent, pathMatch: 'full' },
  { path: '**', component: PageNotFoundComponent, pathMatch: 'full' }];

What I want to know is if it's possible to implement this with lazy loading and if so I'd like to know the main idea or what I need to know in order to do that.

In all the tutorials I did I never encounter this kind of thing. Thank you very much

Answer 1

Thank you everyone for your answers. I managed to convert my routing to lazy loading successfully. This is the code:

app-routing.module

import { NgModule } from '@angular/core';
import { Routes, RouterModule, Router } from '@angular/router';
import { AuthGuard } from './auth.guard';

import { AppComponent } from './app.component';
import { PageNotFoundComponent } from './page-not-found/page-not-found.component';
import { LandingPageComponent } from './landing-page/landing-page.component';
import { HeaderComponent } from './header/header.component';
import { CourseModule } from './courses/course.module';


const routes:Routes = [
  { path: 'welcome', component: LandingPageComponent, pathMatch: 'full' },
  { path: 'login/:id', canActivate: [AuthGuard],  children: [] },
  { path: '', canActivateChild: [AuthGuard], children: [
    { path: '', redirectTo: 'courses', pathMatch: 'full' },
    { path: 'courses',  loadChildren: () => CourseModule }
  ]},
  { path: '**', component: PageNotFoundComponent, pathMatch: 'full' }
]

@NgModule({
  imports: [RouterModule.forRoot(routes, { onSameUrlNavigation: 'reload', initialNavigation: 'enabled',
      paramsInheritanceStrategy: 'always' })],
  providers: [AuthGuard],
  exports: [RouterModule]
})


export class AppRoutingModule {  }

course-routing.module

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from "@angular/router";
import { AuthGuard } from '../auth.guard';

import { CourseListComponent } from './course-list/course-list.component';
import { CourseDetailComponent } from './course-detail/course-detail.component';
import { CoursePlayComponent } from './course-play/course-play.component';
import { CourseQuizComponent } from './course-play/course-quiz/course-quiz.component';
import { CourseLessonComponent } from './course-play/course-lesson/course-lesson.component';


const routes:Routes = [
  { path: '', component: CourseListComponent, canActivate: [AuthGuard] },
  { path: ':courseId', component: CourseDetailComponent, canActivate: [AuthGuard] },
  { path: ':courseId/unit/:unitId', component: CoursePlayComponent, canActivate: [AuthGuard], canActivateChild: [AuthGuard], children: [
    { path: 'lesson/:lessonId', component: CourseLessonComponent, data:{ type: 'lesson'} },
    { path: 'quiz/:quizId', component: CourseQuizComponent, data: {type: 'quiz'}}
  ]}
]

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})
export class CourseRoutingModule { }

auth.guard

import { Injectable } from '@angular/core';
import { Observable, throwError } from 'rxjs';
import { Router, CanActivate, CanActivateChild, CanLoad, ActivatedRouteSnapshot, RouterStateSnapshot, NavigationExtras, Route } from '@angular/router';
import { AuthUserService } from './users/auth-user.service';
import { LocalStorage } from '@ngx-pwa/local-storage';

@Injectable()
export class AuthGuard implements CanActivate , CanActivateChild {

    constructor(private authUserService: AuthUserService, private router: Router) {   }

    canActivate(route: ActivatedRouteSnapshot, state:
       RouterStateSnapshot): boolean |
       Observable<boolean> | Promise<boolean> {
         let id, course_id;

         // save the id from route snapshot
         if (route.params) {
           id = +route.params.id;
           course_id = +route.params.courseId;
         }

         // if you try to logging with id
         if (id) {
           this.router.navigate(["/courses"]);
           return this.authUserService.login(id);
         }

         // if you're already logged in and navigate between pages
         if (this.authUserService.isLoggedIn()){
           if (course_id){
             // check if someone try to access a locked course
             if (this.authUserService.isCourseNotPartOfTheSubscription(course_id)){
               this.router.navigate(["/welcome"]);
               return false;
             }
             else
               return true;
           }
           else
             return true;
         }

         // if you are not logged and didn't try to log - redirect to landing page
         else {
           this.router.navigate(["/welcome"]);
           return false;
         }
        }

      canActivateChild(route: ActivatedRouteSnapshot,state: RouterStateSnapshot): boolean |
      Observable<boolean> | Promise<boolean> {
         return this.canActivate(route, state);
       }

       canLoad(route: ActivatedRouteSnapshot,state: RouterStateSnapshot): boolean |
       Observable<boolean> | Promise<boolean> {
         return this.canActivate(route, state);
       }
}