feat: implementing forFeature (#64)

Add support for module imports using forFeature method in addition to forRoot. This adds the ability for multiple instances of InMemoryDBService to be registered each with differing configurations.

Closes #59

Author: wesleygrimes

README.md

@@ -39,6 +39,8 @@ To get started, let's first update our `app.module.ts` to include the necessary
 
 > While we are importing to the AppModule in this example, InMemoryDBModule could be imported in Feature modules just as well.
 
+#### Registering a forRoot InMemoryDBService
+
 ```typescript
 // app.module.ts
 
@@ -48,7 +50,7 @@ import { InMemoryDBModule } from '@nestjs-addons/in-memory-db';
 
 @Module({
   ...
-  imports: [InMemoryDBModule.forRoot()],
+  imports: [InMemoryDBModule.forRoot({})],
   ...
 })
 export class AppModule {}
@@ -102,6 +104,53 @@ export class UserController {
 }
 ```
 
+## Feature Modules - Registering Multiple Instances using `forFeature`
+
+Registering multiple instances for specific feature modules is super simple. Each feature module is guaranteed isolated to that feature. In order to get up and running you need to do the following:
+
+#### Registering a forFeature InMemoryDBService
+
+For each feature module(s), do the following:
+
+```typescript
+// feature-one.module.ts
+
+import { Module } from '@nestjs/common';
+import { InMemoryDBModule } from '@nestjs-addons/in-memory-db';
+...
+
+@Module({
+  ...
+  imports: [InMemoryDBModule.forFeature('one', {})],
+  ...
+})
+export class FeatureOneModule {}
+```
+
+As you can see we:
+
+- Imported `InMemoryDBModule` from `@nestjs-addons/in-memory-db`
+- Added `InMemoryDBModule` to the `imports` array in the `@Module` of your choice
+- Added the `forFeature` method call passing `one` as the feature name
+
+#### Using the Feature Instance
+
+If you would like to use the feature-specific instance, make use of the included `@InjectInMemoryDBService` decorator:
+
+```typescript
+@Controller({...})
+export class FeatureOneController {
+  constructor(@InjectInMemoryDBService('one') private oneService: InMemoryDBService<OneEntity>) {}
+  ...
+  @Get()
+  getAll(): OneEntity[] {
+    return this.oneService.getAll();
+  }
+}
+```
+
+Using this decorator ensures that the correct instance is injected.
+
 ## Docs
 
 [Click here for more detailed API Documentation](API.md)

lib/common/in-memory-db.constants.ts

@@ -0,0 +1,2 @@
+export const IN_MEMORY_DB_SERVICE = 'InMemoryDBService';
+export const IN_MEMORY_DB_CONFIG = 'InMemoryDBConfig';

lib/common/in-memory-db.decorators.ts

@@ -0,0 +1,5 @@
+import { Inject } from '@nestjs/common';
+import { getInMemoryDBServiceToken } from './in-memory-db.utils';
+
+export const InjectInMemoryDBService = (featureName: string) =>
+  Inject(getInMemoryDBServiceToken(featureName));

lib/common/in-memory-db.utils.spec.ts

@@ -0,0 +1,19 @@
+import { getInMemoryDBServiceToken } from './in-memory-db.utils';
+
+describe('getInMemoryDBServiceToken', () => {
+  test.each([
+    ['oneInMemoryDBService', 'one'],
+    ['InMemoryDBService', ''],
+    ['InMemoryDBService', null],
+    ['InMemoryDBService', undefined],
+  ])(
+    'should return %p token given input featureName of %p',
+    (expectedToken: string, featureName: string) => {
+      // act
+      const actualToken = getInMemoryDBServiceToken(featureName);
+
+      // assert
+      expect(actualToken).toEqual(expectedToken);
+    },
+  );
+});

lib/common/in-memory-db.utils.ts

@@ -0,0 +1,7 @@
+import { IN_MEMORY_DB_SERVICE } from './in-memory-db.constants';
+
+export function getInMemoryDBServiceToken(featureName?: string) {
+  return featureName && featureName !== IN_MEMORY_DB_SERVICE
+    ? `${featureName}${IN_MEMORY_DB_SERVICE}`
+    : IN_MEMORY_DB_SERVICE;
+}

lib/common/index.ts

@@ -0,0 +1,2 @@
+export * from './in-memory-db.decorators';
+export { getInMemoryDBServiceToken } from './in-memory-db.utils';

lib/factories/in-memory-db-service.factory.ts

@@ -0,0 +1,15 @@
+import { InMemoryDBConfig, InMemoryDBEntity } from '../interfaces';
+import { InMemoryDBService } from '../services';
+
+export function inMemoryDBServiceFactory<T extends InMemoryDBEntity>(
+  featureConfig: Partial<InMemoryDBConfig> = {},
+  featureName?: string,
+) {
+  return () =>
+    new InMemoryDBService<T>({
+      featureName: featureName
+        ? featureName
+        : featureConfig.featureName || 'root',
+      ...featureConfig,
+    });
+}

lib/factories/index.ts

@@ -0,0 +1 @@
+export * from './in-memory-db-service.factory';

lib/in-memory-db.module.ts

@@ -2,22 +2,33 @@ import { DynamicModule, Module } from '@nestjs/common';
 
 import { InMemoryDBConfig } from './interfaces';
 import { InMemoryDBService } from './services';
-
+import {
+  createInMemoryDBForRootProviders,
+  createInMemoryDBForFeatureProviders,
+} from './providers';
 @Module({
   providers: [InMemoryDBService],
   exports: [InMemoryDBService],
 })
 export class InMemoryDBModule {
   public static forRoot(config: Partial<InMemoryDBConfig> = {}): DynamicModule {
+    const providers = createInMemoryDBForRootProviders(config);
+    return {
+      module: InMemoryDBModule,
+      providers,
+      exports: providers,
+    };
+  }
+
+  public static forFeature(
+    featureName: string,
+    config: Partial<InMemoryDBConfig> = {},
+  ): DynamicModule {
+    const providers = createInMemoryDBForFeatureProviders(featureName, config);
     return {
       module: InMemoryDBModule,
-      providers: [
-        {
-          provide: InMemoryDBService,
-          useValue: new InMemoryDBService(config),
-        },
-      ],
-      exports: [InMemoryDBService],
+      providers,
+      exports: providers,
     };
   }
 }

lib/index.ts

@@ -1,4 +1,7 @@
 import 'reflect-metadata';
+import { InjectInMemoryDBService } from './common';
+
 export * from './in-memory-db.module';
 export * from './interfaces';
 export * from './services';
+export { InjectInMemoryDBService };