使用相同token，指定多種provider

src/app/a/a.module.ts

@@ -0,0 +1,11 @@
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+
+@NgModule({
+  imports: [
+    CommonModule
+  ],
+  declarations: [],
+  providers: [{ provide: 'i18nFolder', useValue: 'a-module', multi: true }]
+})
+export class AModule { }

src/app/app.component.html

@@ -1,14 +1,2 @@
-<table border="1">
-  <tr>
-    <th>單價</th>
-    <th>數量</th>
-  </tr>
-  <tr *ngFor="let item of orderService.details">
-    <td>{{ item.UnitPrice }}</td>
-    <td>{{ item.PurchaseCount }}</td>
-  </tr>
-  <tr>
-    <td>總金額</td>
-    <td>{{ total }}</td>
-  </tr>
-</table>
+<h3>多個 i18n 資料夾設定</h3>
+<pre>{{ i18nService.i18nFolder | json }}</pre>

src/app/app.component.ts

@@ -1,24 +1,12 @@
-import { Component, Inject, OnInit } from '@angular/core';
+import { Component, VERSION } from '@angular/core';
 
-import { OrderDetail } from './order-detail';
-import { IOrderService, ORDER_SERVICE } from './order.interface';
+import { I18nService } from './i18n.service';
 
 @Component({
   selector: 'my-app',
   templateUrl: './app.component.html',
-  styleUrls: ['./app.component.css'],
+  styleUrls: [ './app.component.css' ]
 })
-export class AppComponent implements OnInit {
-  total = 0;
-
-  //@Inject 注入Service(ORDER_SERVICE) Token
-  constructor(@Inject(ORDER_SERVICE) public orderService: IOrderService) {}
-
-  ngOnInit(): void {
-    this.orderService.details = [
-      new OrderDetail({ PurchaseCount: 2, UnitPrice: 200 }),
-      new OrderDetail({ PurchaseCount: 4, UnitPrice: 50 }),
-    ];
-    this.total = this.orderService.computeTotal();
-  }
+export class AppComponent  {
+  constructor(public i18nService: I18nService) {}
 }

src/app/app.module.ts

@@ -3,13 +3,12 @@ import { BrowserModule } from '@angular/platform-browser';
 import { FormsModule } from '@angular/forms';
 
 import { AppComponent } from './app.component';
-import { ORDER_SERVICE } from './order.interface';
-import { OrderService } from './order.service';
+import { AModule } from './a/a.module';
+import { BModule } from './b/b.module';
 
 @NgModule({
-  imports: [BrowserModule, FormsModule],
-  declarations: [AppComponent],
-  providers: [{ provide: ORDER_SERVICE, useClass: OrderService }],
-  bootstrap: [AppComponent],
+  imports:      [ BrowserModule, FormsModule, AModule, BModule ],
+  declarations: [ AppComponent ],
+  bootstrap:    [ AppComponent ]
 })
-export class AppModule {}
+export class AppModule { }

src/app/b/b.module.ts

@@ -0,0 +1,11 @@
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+
+@NgModule({
+  imports: [
+    CommonModule
+  ],
+  declarations: [],
+  providers: [{ provide: 'i18nFolder', useValue: 'b-module', multi: true }]
+})
+export class BModule { }

src/app/i18n.service.ts

@@ -0,0 +1,12 @@
+import { Inject, Injectable } from '@angular/core';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class I18nService {
+  i18nFolder: string[];
+
+  constructor(@Inject('i18nFolder') folders: string[]) {
+    this.i18nFolder = folders.map((folder) => `assets/${folder}`);
+  }
+}

src/app/order-detail.ts

@@ -1,9 +0,0 @@
-export class OrderDetail {
-  constructor(initData?: Partial<OrderDetail>) {
-    Object.assign(this, initData);
-  }
-
-  PurchaseCount!: number;
-
-  UnitPrice!: number;
-}

src/app/order.interface.ts

@@ -1,8 +0,0 @@
-import { InjectionToken } from "@angular/core";
-import { OrderDetail } from "./order-detail";
-export const ORDER_SERVICE = new InjectionToken<IOrderService>('Order Service');
-
-export interface IOrderService {
-  details: OrderDetail[];
-  computeTotal():number;
-}

src/app/order.service.ts

@@ -1,19 +0,0 @@
-import { Injectable } from '@angular/core';
-
-import { OrderDetail } from './order-detail';
-import { IOrderService } from './order.interface';
-
-@Injectable({
-  providedIn: 'root',
-})
-export class OrderService implements IOrderService {
-  details: OrderDetail[] = [];
-
-  constructor() {}
-
-  computeTotal(): number {
-    return this.details
-      .map((d) => d.PurchaseCount * d.UnitPrice)
-      .reduce((act, curr) => act + curr, 0);
-  }
-}