我正在尝试创建一个提供单例服务的模块。想象一下QueueService
,最简单的实现是单例服务。
可复制的存储库:https://github.com/colthreepv/nestjs-singletons
代码墙
app.module.ts:
@Module({ imports: [FirstConsumerModule, SecondConsumerModule] })
export class AppModule {}
firstconsumer.module.ts 和 secondconsumer.module.ts(它们是相同的):
@Injectable()
class FirstConsumer {
constructor(private readonly dependency: DependencyService) {}
}
@Module({
imports: [DependencyServiceModule],
providers: [DependencyService, FirstConsumer]
})
export class FirstConsumerModule {
constructor(private readonly first: FirstConsumer) {}
}
dependency.module.ts:
@Injectable()
export class DependencyService {
constructor() { console.log("Instance created") }
}
@Module({ providers: [DependencyService], exports: [DependencyService] })
export class DependencyServiceModule {}
代码已完成
我想获得的是console.log Instance created
仅发布一次。
目前:
[NestFactory] Starting Nest application...
Instance created
Instance created
Instance created
[InstanceLoader] AppModule dependencies initialized +16ms
[InstanceLoader] DependencyServiceModule dependencies initialized +1ms
[InstanceLoader] FirstConsumerModule dependencies initialized +1ms
[InstanceLoader] SecondConsumerModule dependencies initialized +1ms
[NestApplication] Nest application successfully started +8ms
答案 0 :(得分:6)
在NestJS模块中,单身人士及其提供者被制成单身人士,只要它们是从同一模块中提供的。在示例代码中,您将DependencyService
放在三个不同的providers
数组中,用于三个不同的模块。相反,应该仅将其保存在providers
和DependencyServiceModule
数组的exports
数组中。然后,您只需要在DependencyServiceModule
和imports
的{{1}}数组中放置FrstConsumerModule
,并且不需要添加SecondConsumerModule
到任一的DependencyService
数组。由于位于providers
数组中,因此提供程序已可用于模块上下文。
exports
@Module({
providers: [DependencyService],
exports: [DependencyService]
})
export class DependencyServiceModule {}
@Module({
imports: [DependencyServiceModule],
providers: [FirstConsumer] // notice no DependencyService class
})
export class FirstConsumerModule {}
通过以上内容,您只会看到一个“创建实例”日志,而不是两个。