@toss/nestjs-aop ·

A way to gracefully apply AOP to NestJS.
Use NestJS managed instances in any decorators gracefully.

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Table of Contents

1. Installation
2. Usage
3. Caveats
4. References
5. Contributing
6. License

Installation

npm install @toss/nestjs-aop
pnpm add @toss/nestjs-aop
yarn add @toss/nestjs-aop

Usage

1. Import AopModule

@Module({
  imports: [
    // ...
    AopModule,
  ],
})
export class AppModule {}

2. Create symbol for LazyDecorator

export const CACHE_DECORATOR = Symbol('CACHE_DECORATOR');

3. Implement LazyDecorator using nestjs provider

metadata is passed as the second argument to createDecorator and is made available in the WrapParams for the wrap method.

@Aspect(CACHE_DECORATOR)
export class CacheDecorator implements LazyDecorator<any, CacheOptions> {
  constructor(private readonly cache: Cache) {}

  wrap({ method, metadata: options }: WrapParams<any, CacheOptions>) {
    return (...args: any) => {
      let cachedValue = this.cache.get(...args);
      if (!cachedValue) { 
        cachedValue = method(...args);
        this.cache.set(cachedValue, ...args);
      }
      return cachedValue;
    };
  }
}

4. Add LazyDecoratorImpl to providers of module

@Module({
  providers: [CacheDecorator],
})
export class CacheModule {}

5. Create decorator that marks metadata of LazyDecorator

options can be obtained from the wrap method and used.

export const Cache = (options: CacheOptions) => createDecorator(CACHE_DECORATOR, options)

6. Use it!

export class SomeService {
  @Cache({
    // ...options(metadata value)
  })
  some() {
    // ...
  }
}

Caveats

If you’re testing with NestJS’s TestingModule, don’t forget to call the init method.

import { Test } from '@nestjs/testing';

const module = await Test.createTestingModule({
  // ...
}).compile();

await module.init();

References

• https://toss.tech/article/nestjs-custom-decorator
• https://youtu.be/VH1GTGIMHQw?t=2973

Contributing

We welcome contributions from everyone to this project. Read CONTRIBUTING.md for detailed contribution guide.

License

MIT © Viva Republica, Inc. See LICENSE for details.