Pupli

import { CommonModule } from '@angular/common';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { CustomerComponent } from './customer.component';
import { NewItemDirective } from './new-item.directive';
import { OrdersPipe } from './orders.pipe';

@NgModule({
 imports:      [ CommonModule ],
 declarations: [ CustomerComponent, NewItemDirective, OrdersPipe ],
 exports:      [ CustomerComponent, NewItemDirective, OrdersPipe,
                 CommonModule, FormsModule ]
})
export class SharedModule { }

References
https://angular.io/guide/sharing-ngmodules

ng generate module customers --route customer-list --module app.module

tsconfig.app.json & tsconfig.json

"module": "esnext"

References
https://angular.io/guide/lazy-loading-ngmodules

import { Component, forwardRef, HostBinding, Input } from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';

@Component({
  selector: 'rating-input',
  template: `
    <span
      *ngFor="let starred of stars; let i = index"
      (click)="onTouched(); rate(i + (starred ? (value > i + 1 ? 1 : 0) : 1))">
      <ng-container *ngIf="starred; else noStar">⭐</ng-container>
      <ng-template #noStar>·</ng-template>
    </span>
  `,
  styles: [`
    span {
      display: inline-block;
      width: 25px;
      line-height: 25px;
      text-align: center;
      cursor: pointer;
    }
  `],
  providers: [
    {
      provide: NG_VALUE_ACCESSOR,
      useExisting: forwardRef(() => RatingInputComponent),
      multi: true
    }
  ]
})
export class RatingInputComponent implements ControlValueAccessor {

  stars: boolean[] = Array(5).fill(false);

  // Allow the input to be disabled, and when it is make it somewhat transparent.
  @Input() disabled = false;
  @HostBinding('style.opacity')
  get opacity() {
    return this.disabled ? 0.25 : 1;
  }

  // Function to call when the rating changes.
  onChange = (rating: number) => {};

  // Function to call when the input is touched (when a star is clicked).
  onTouched = () => {};

  get value(): number {
    return this.stars.reduce((total, starred) => {
      return total + (starred ? 1 : 0);
    }, 0);
  }

  rate(rating: number) {
    if (!this.disabled) {
      this.writeValue(rating);
    }
  }

  // Allows Angular to update the model (rating).
  // Update the model and changes needed for the view here.
  writeValue(rating: number): void {
    this.stars = this.stars.map((_, i) => rating > i);
    this.onChange(this.value)
  }

  // Allows Angular to register a function to call when the model (rating) changes.
  // Save the function as a property to call later here.
  registerOnChange(fn: (rating: number) => void): void {
    this.onChange = fn;
  }

  // Allows Angular to register a function to call when the input has been touched.
  // Save the function as a property to call later here.
  registerOnTouched(fn: () => void): void {
    this.onTouched = fn;
  }

  // Allows Angular to disable the input.
  setDisabledState(isDisabled: boolean): void {
    this.disabled = isDisabled;
  }

}

References
https://alligator.io/angular/custom-form-control/
https://blog.thoughtram.io/angular/2016/07/27/custom-form-controls-in-angular-2.html

As the name suggests, we can add a resolve function to the route which loads the component that has an API call to do. This will cause the component to be only loaded and displayed by Angular once the API call (or whatever else we define) is loaded.

Create a separate class which we’ll have the resolver functionality

// resolver.ts
import { Injectable } from '@angular/core';
import { Resolve } from '@angular/router';
import { Observable } from 'rxjs';
import { ApiService } from './api.service';

@Injectable()
export class Resolver implements Resolve<Observable<string>> {
  constructor(private api: ApiService) { }

  resolve() {
    return this.api.getProducts();
  }
}

Add this class as a provider

// app.module.ts
import { Resolver } from './resolver';
// ...
providers: [Resolver],

app-routing.module.ts

// app-routing.module.ts
import { Resolver } from './resolver';

const routes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'products', component: ProductsComponent, resolve: { products: Resolver } }
];

// products.component.ts
import { ActivatedRoute } from '@angular/router';
// ...
constructor(private route: ActivatedRoute) { }
products;
ngOnInit() {
  this.products = this.route.snapshot.data.products;
}

Access to Route Params

import { Injectable } from '@angular/core';
import { HnService } from './hn.service';

import { Resolve } from '@angular/router';

import { ActivatedRouteSnapshot } from '@angular/router';

@Injectable()
export class HnResolver implements Resolve<any> {
  constructor(private hnService: HnService) {}

  resolve(route: ActivatedRouteSnapshot) {
    return this.hnService.getPost(route.paramMap.get('id'));
  }
}

References
https://blog.fullstacktraining.com/loading-data-before-components-in-angular/
https://alligator.io/angular/route-resolvers/