feat: add post on Lazy Loading routes using an Observable

angular.json

@@ -137,6 +137,109 @@
           }
         }
       }
+    },
+    "observable-load-children": {
+      "projectType": "application",
+      "schematics": {
+        "@schematics/angular:component": {
+          "inlineTemplate": true,
+          "inlineStyle": true,
+          "style": "sass",
+          "skipTests": true
+        },
+        "@schematics/angular:class": {
+          "skipTests": true
+        },
+        "@schematics/angular:directive": {
+          "skipTests": true
+        },
+        "@schematics/angular:guard": {
+          "skipTests": true
+        },
+        "@schematics/angular:interceptor": {
+          "skipTests": true
+        },
+        "@schematics/angular:module": {
+          "skipTests": true
+        },
+        "@schematics/angular:pipe": {
+          "skipTests": true
+        },
+        "@schematics/angular:service": {
+          "skipTests": true
+        }
+      },
+      "root": "apps/observable-load-children",
+      "sourceRoot": "apps/observable-load-children/src",
+      "prefix": "app",
+      "architect": {
+        "build": {
+          "builder": "@angular-devkit/build-angular:browser",
+          "options": {
+            "outputPath": "dist/observable-load-children",
+            "index": "apps/observable-load-children/src/index.html",
+            "main": "apps/observable-load-children/src/main.ts",
+            "polyfills": "apps/observable-load-children/src/polyfills.ts",
+            "tsConfig": "apps/observable-load-children/tsconfig.app.json",
+            "aot": true,
+            "assets": [
+              "apps/observable-load-children/src/favicon.ico",
+              "apps/observable-load-children/src/assets"
+            ],
+            "styles": [
+              "apps/observable-load-children/src/styles.sass"
+            ],
+            "scripts": []
+          },
+          "configurations": {
+            "production": {
+              "fileReplacements": [
+                {
+                  "replace": "apps/observable-load-children/src/environments/environment.ts",
+                  "with": "apps/observable-load-children/src/environments/environment.prod.ts"
+                }
+              ],
+              "optimization": true,
+              "outputHashing": "all",
+              "sourceMap": false,
+              "extractCss": true,
+              "namedChunks": false,
+              "extractLicenses": true,
+              "vendorChunk": false,
+              "buildOptimizer": true,
+              "budgets": [
+                {
+                  "type": "initial",
+                  "maximumWarning": "2mb",
+                  "maximumError": "5mb"
+                },
+                {
+                  "type": "anyComponentStyle",
+                  "maximumWarning": "6kb",
+                  "maximumError": "10kb"
+                }
+              ]
+            }
+          }
+        },
+        "serve": {
+          "builder": "@angular-devkit/build-angular:dev-server",
+          "options": {
+            "browserTarget": "observable-load-children:build"
+          },
+          "configurations": {
+            "production": {
+              "browserTarget": "observable-load-children:build:production"
+            }
+          }
+        },
+        "extract-i18n": {
+          "builder": "@angular-devkit/build-angular:extract-i18n",
+          "options": {
+            "browserTarget": "observable-load-children:build"
+          }
+        }
+      }
     }
   },
   "defaultProject": "blog"

apps/observable-load-children/browserslist

@@ -0,0 +1,12 @@
+# This file is used by the build system to adjust CSS and JS output to support the specified browsers below.
+# For additional information regarding the format and rule options, please see:
+# https://github.com/browserslist/browserslist#queries
+
+# You can see what browsers were selected by your queries by running:
+#   npx browserslist
+
+> 0.5%
+last 2 versions
+Firefox ESR
+not dead
+not IE 9-11 # For IE 9-11 support, remove 'not'.

apps/observable-load-children/src/app/app-routing.module.1.ts

@@ -0,0 +1,14 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+const routes: Routes = [
+  { path: 'lazy', loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule) },
+  { path: '', redirectTo: 'lazy', pathMatch: 'full' }
+];
+
+@NgModule({
+  imports: [
+    RouterModule.forRoot(routes)  
+  ],
+})
+export class AppRoutingModule { }

apps/observable-load-children/src/app/app-routing.module.2.ts

@@ -0,0 +1,25 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+import { Observable } from 'rxjs';
+
+const routes: Routes = [
+  {
+    path: 'lazy', loadChildren: () => new Observable(observer => {
+      import('./lazy/lazy.module').then(m => {
+        observer.next(m.LazyModule);
+        observer.complete();
+      }, error => {
+        observer.error(error);
+      })
+    })
+  },
+  { path: '', redirectTo: 'lazy', pathMatch: 'full' }
+];
+
+@NgModule({
+  imports: [
+    RouterModule.forRoot(routes)  
+  ],
+})
+export class AppRoutingModule { }

apps/observable-load-children/src/app/app-routing.module.3.ts

@@ -0,0 +1,17 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+import { from } from 'rxjs';
+import { map } from 'rxjs/operators';
+
+const routes: Routes = [
+  { path: 'lazy', loadChildren: () => from(import('./lazy/lazy.module')).pipe(map(m => m.LazyModule)) },
+  { path: '', redirectTo: 'lazy', pathMatch: 'full' }
+];
+
+@NgModule({
+  imports: [
+    RouterModule.forRoot(routes)  
+  ],
+})
+export class AppRoutingModule { }

apps/observable-load-children/src/app/app-routing.module.4.ts

@@ -0,0 +1,26 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+import { from } from 'rxjs';
+import { map, tap } from 'rxjs/operators';
+
+const routes: Routes = [
+  {
+    path: 'lazy', loadChildren: () => from(import('./lazy/lazy.module')).pipe(
+      map(m => m.LazyModule),
+      tap(() => {
+        console.log('Lazy Module Loaded');
+      }, () => {
+        console.log('Lazy Module Load Failed');
+      })
+    )
+  },
+  { path: '', redirectTo: 'lazy', pathMatch: 'full' }
+];
+
+@NgModule({
+  imports: [
+    RouterModule.forRoot(routes)
+  ],
+})
+export class AppRoutingModule { }

apps/observable-load-children/src/app/app-routing.module.ts

@@ -0,0 +1,23 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+import { defer } from 'rxjs';
+import { map, retry, tap } from 'rxjs/operators';
+
+
+const routes: Routes = [
+  {
+    path: 'lazy',
+    loadChildren: () => defer(() => import('./lazy/lazy.module')).pipe(
+      map(m => m.LazyModule),
+      retry(2)
+    )
+  },
+  { path: '', redirectTo: 'lazy', pathMatch: 'full' }
+];
+
+@NgModule({
+  imports: [
+    RouterModule.forRoot(routes)
+  ]
+})
+export class AppRoutingModule { }

apps/observable-load-children/src/app/app.component.ts

@@ -0,0 +1,32 @@
+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'app-root',
+  template: `
+    <!--The content below is only a placeholder and can be replaced.-->
+    <div style="text-align:center" class="content">
+      <h1>
+        Welcome to {{title}}!
+      </h1>
+      <span style="display: block">{{ title }} app is running!</span>
+      <img width="300" alt="Angular Logo" src="data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNTAgMjUwIj4KICAgIDxwYXRoIGZpbGw9IiNERDAwMzEiIGQ9Ik0xMjUgMzBMMzEuOSA2My4ybDE0LjIgMTIzLjFMMTI1IDIzMGw3OC45LTQzLjcgMTQuMi0xMjMuMXoiIC8+CiAgICA8cGF0aCBmaWxsPSIjQzMwMDJGIiBkPSJNMTI1IDMwdjIyLjItLjFWMjMwbDc4LjktNDMuNyAxNC4yLTEyMy4xTDEyNSAzMHoiIC8+CiAgICA8cGF0aCAgZmlsbD0iI0ZGRkZGRiIgZD0iTTEyNSA1Mi4xTDY2LjggMTgyLjZoMjEuN2wxMS43LTI5LjJoNDkuNGwxMS43IDI5LjJIMTgzTDEyNSA1Mi4xem0xNyA4My4zaC0zNGwxNy00MC45IDE3IDQwLjl6IiAvPgogIDwvc3ZnPg==">
+    </div>
+    <h2>Here are some links to help you start: </h2>
+    <ul>
+      <li>
+        <h2><a target="_blank" rel="noopener" href="https://angular.io/tutorial">Tour of Heroes</a></h2>
+      </li>
+      <li>
+        <h2><a target="_blank" rel="noopener" href="https://angular.io/cli">CLI Documentation</a></h2>
+      </li>
+      <li>
+        <h2><a target="_blank" rel="noopener" href="https://blog.angular.io/">Angular blog</a></h2>
+      </li>
+    </ul>
+    <router-outlet></router-outlet>
+  `,
+  styles: []
+})
+export class AppComponent {
+  title = 'observable-load-children';
+}

apps/observable-load-children/src/app/app.module.ts

@@ -0,0 +1,20 @@
+import { BrowserModule } from '@angular/platform-browser';
+import { NgModule } from '@angular/core';
+import { RouterModule } from '@angular/router';
+
+import { AppRoutingModule } from './app-routing.module';
+import { AppComponent } from './app.component';
+
+@NgModule({
+  declarations: [
+    AppComponent
+  ],
+  imports: [
+    BrowserModule,
+    AppRoutingModule,
+    RouterModule
+  ],
+  providers: [],
+  bootstrap: [AppComponent]
+})
+export class AppModule { }

apps/observable-load-children/src/app/lazy/lazy-routing.module.ts

@@ -0,0 +1,12 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+import { LazyComponent } from './lazy.component';
+
+const routes: Routes = [{ path: '', component: LazyComponent }];
+
+@NgModule({
+  imports: [RouterModule.forChild(routes)],
+  exports: [RouterModule]
+})
+export class LazyRoutingModule { }

apps/observable-load-children/src/app/lazy/lazy.component.ts

@@ -0,0 +1,20 @@
+import { Component, OnInit } from '@angular/core';
+
+@Component({
+  selector: 'app-lazy',
+  template: `
+    <p>
+      lazy works!
+    </p>
+  `,
+  styles: [
+  ]
+})
+export class LazyComponent implements OnInit {
+
+  constructor() { }
+
+  ngOnInit(): void {
+  }
+
+}

apps/observable-load-children/src/app/lazy/lazy.module.ts

@@ -0,0 +1,15 @@
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+
+import { LazyRoutingModule } from './lazy-routing.module';
+import { LazyComponent } from './lazy.component';
+
+
+@NgModule({
+  declarations: [LazyComponent],
+  imports: [
+    CommonModule,
+    LazyRoutingModule
+  ]
+})
+export class LazyModule { }

apps/observable-load-children/src/environments/environment.prod.ts

@@ -0,0 +1,3 @@
+export const environment = {
+  production: true
+};

apps/observable-load-children/src/environments/environment.ts

@@ -0,0 +1,16 @@
+// This file can be replaced during build by using the `fileReplacements` array.
+// `ng build --prod` replaces `environment.ts` with `environment.prod.ts`.
+// The list of file replacements can be found in `angular.json`.
+
+export const environment = {
+  production: false
+};
+
+/*
+ * For easier debugging in development mode, you can import the following file
+ * to ignore zone related error stack frames such as `zone.run`, `zoneDelegate.invokeTask`.
+ *
+ * This import should be commented out in production mode because it will have a negative impact
+ * on performance if an error is thrown.
+ */
+// import 'zone.js/dist/zone-error';  // Included with Angular CLI.

apps/observable-load-children/src/index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>ObservableLoadChildren</title>
+  <base href="/">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <link rel="icon" type="image/x-icon" href="favicon.ico">
+</head>
+<body>
+  <app-root></app-root>
+</body>
+</html>

apps/observable-load-children/src/main.ts

@@ -0,0 +1,12 @@
+import { enableProdMode } from '@angular/core';
+import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
+
+import { AppModule } from './app/app.module';
+import { environment } from './environments/environment';
+
+if (environment.production) {
+  enableProdMode();
+}
+
+platformBrowserDynamic().bootstrapModule(AppModule)
+  .catch(err => console.error(err));