Answer:54

apps/signal/54-pipe-observable-to-signal/src/app/currency.pipe.ts

@@ -1,5 +1,4 @@
 import { inject, Pipe, PipeTransform } from '@angular/core';
-import { map, Observable } from 'rxjs';
 import { CurrencyService } from './currency.service';
 
 @Pipe({
@@ -9,7 +8,8 @@ import { CurrencyService } from './currency.service';
 export class CurrencyPipe implements PipeTransform {
   currencyService = inject(CurrencyService);
 
-  transform(price: number): Observable<string> {
-    return this.currencyService.symbol$.pipe(map((s) => `${price}${s}`));
+  transform(price: number): string {
+    const symbol = this.currencyService.symbol();
+    return `${price}${symbol}`;
   }
 }

apps/signal/54-pipe-observable-to-signal/src/app/currency.service.ts

@@ -1,5 +1,4 @@
-import { Injectable } from '@angular/core';
-import { BehaviorSubject, map } from 'rxjs';
+import { computed, Injectable, signal } from '@angular/core';
 
 export interface Currency {
   name: string;
@@ -17,14 +16,14 @@ export const currency: Currency[] = [
 
 @Injectable()
 export class CurrencyService {
-  private code = new BehaviorSubject('EUR');
+  private code = signal('EUR');
 
-  readonly code$ = this.code.asObservable();
-  readonly symbol$ = this.code$.pipe(
-    map((code) => currency.find((c) => c.code === code)?.symbol ?? code),
-  );
+  readonly symbol = computed(() => {
+    const current = this.code();
+    return currency.find((c) => c.code === current)?.symbol ?? current;
+  });
 
-  public updateCode(code: string) {
-    this.code.next(code);
+  updateCode(newCode: string) {
+    this.code.set(newCode);
   }
 }

apps/signal/54-pipe-observable-to-signal/src/app/product-row.component.ts

@@ -1,4 +1,3 @@
-import { AsyncPipe } from '@angular/common';
 import {
   ChangeDetectionStrategy,
   Component,
@@ -13,11 +12,11 @@ import { Product } from './product.model';
   selector: 'tr[product-row]',
   template: `
     <td>{{ productInfo.name }}</td>
-    <td>{{ productInfo.priceA | currency | async }}</td>
-    <td>{{ productInfo.priceB | currency | async }}</td>
-    <td>{{ productInfo.priceC | currency | async }}</td>
+    <td>{{ productInfo.priceA | currency }}</td>
+    <td>{{ productInfo.priceB | currency }}</td>
+    <td>{{ productInfo.priceC | currency }}</td>
   `,
-  imports: [AsyncPipe, CurrencyPipe],
+  imports: [CurrencyPipe],
   providers: [CurrencyService],
   changeDetection: ChangeDetectionStrategy.OnPush,
 })