Issue with implementing generic inheritance for Repository in NestJS TypeORM: `this.function` is returning an error as it is not

Question

Issue with implementing generic inheritance for Repository in NestJS TypeORM: `this.function` is returning an error as it is not

I am attempting to create a specialized repository class that extends Repository in order to incorporate custom logging functions that can be utilized across all repositories. Here is the snippet of code:

user.service.ts:

@Injectable()
export class UserService {
    constructor(
        @InjectRepository(User)
        private readonly userRepository: BaseRepository<User>,
    ) {}

    async update(id: string, data: UpdateUserDto): Promise<UpdateResult> {
        return await this.userRepository.updateAndLog(id, data);
    }
}

BaseRepository.ts:

import { Repository, UpdateResult } from 'typeorm';


export class BaseRepository<T> extends Repository<T> {

  async updateAndLog(id: string, data: any): Promise<UpdateResult> {
    const entity = await this.findOne(id as any);
    const savedEntity = await this.update(id, data);
    // log the data here
    return savedEntity;
  }
}

Therefore, the outcome of the function always displays:

[Nest] 13820  - 04/11/2023, 12:07:07 PM   ERROR [ExceptionsHandler] this.userRepository.updateAndLog is not a function

I have carefully reviewed the typeorm documentation regarding custom repositories:

Additional resources from StackOverflow:

How to do custom repository using TypeORM (MongoDB) in NestJS?
NestJS/TypeORM: Can custom repository extend from another custom repository which is inside another project?

View the repository on github: https://github.com/typeorm/typeorm/issues/2097

Despite my efforts, the code provided above is not functioning as expected. Is there an issue I may have overlooked?

typescript oop nestjs typeorm

Answer 1

Answer №1

The issue arises from using @InjectRepository(User) which injects a Repository instance instead of the desired BaseRepository.

I stumbled upon this particular repository that offers a solution to override the repository provided by the TypeORM module, but only for a specific entity.

We can tweak this approach to provide a generic repository like so:

@Module({
  imports: [TypeOrmModule.forFeature([User])],
  providers: [buildCustomRepositoryProvider<User>(User), UserService],
})
export class UserModule {
}

A helper file for this purpose:

import { DataSource, Repository, UpdateResult } from 'typeorm';
import { Provider } from '@nestjs/common';
import { getDataSourceToken, getRepositoryToken } from '@nestjs/typeorm';
import { EntityClassOrSchema } from '@nestjs/typeorm/dist/interfaces/entity-class-or-schema.type';

export interface BaseRepository<T> extends Repository<T> {
  this: Repository<T>;

  updateAndLog(id: string, data: any): Promise<UpdateResult>;
}

export function buildCustomRepositoryMethods<T>(): Pick<BaseRepository<T>, 'updateAndLog'> {
  return {
    async updateAndLog(id: string, data: any): Promise<UpdateResult> {
      const entity = await this.findOne({ where: { id: id as any } });
      const savedEntity = await this.update(id, data);
      // log the data here
      return savedEntity;
    },
  };
}

export function buildCustomRepositoryProvider<T>(entity: EntityClassOrSchema): Provider {
  return {
    provide: getRepositoryToken(entity),
    inject: [getDataSourceToken()],
    useFactory: (dataSource: DataSource) => {
      // Override the default repository with a custom one
      return dataSource.getRepository(entity).extend(buildCustomRepositoryMethods<T>());
    },
  };
}

Consequently, the @InjectRepository(User) will now inject an instance of Repository<User> with the methods from the BaseRepository interface.

(Please note: the use of the extend method to create a custom repository is recommended since TypeORM 0.3, as mentioned here)

Answer 2

The issue arises from using @InjectRepository(User) which injects a Repository instance instead of the desired BaseRepository.

I stumbled upon this particular repository that offers a solution to override the repository provided by the TypeORM module, but only for a specific entity.

We can tweak this approach to provide a generic repository like so:

@Module({
  imports: [TypeOrmModule.forFeature([User])],
  providers: [buildCustomRepositoryProvider<User>(User), UserService],
})
export class UserModule {
}

A helper file for this purpose:

import { DataSource, Repository, UpdateResult } from 'typeorm';
import { Provider } from '@nestjs/common';
import { getDataSourceToken, getRepositoryToken } from '@nestjs/typeorm';
import { EntityClassOrSchema } from '@nestjs/typeorm/dist/interfaces/entity-class-or-schema.type';

export interface BaseRepository<T> extends Repository<T> {
  this: Repository<T>;

  updateAndLog(id: string, data: any): Promise<UpdateResult>;
}

export function buildCustomRepositoryMethods<T>(): Pick<BaseRepository<T>, 'updateAndLog'> {
  return {
    async updateAndLog(id: string, data: any): Promise<UpdateResult> {
      const entity = await this.findOne({ where: { id: id as any } });
      const savedEntity = await this.update(id, data);
      // log the data here
      return savedEntity;
    },
  };
}

export function buildCustomRepositoryProvider<T>(entity: EntityClassOrSchema): Provider {
  return {
    provide: getRepositoryToken(entity),
    inject: [getDataSourceToken()],
    useFactory: (dataSource: DataSource) => {
      // Override the default repository with a custom one
      return dataSource.getRepository(entity).extend(buildCustomRepositoryMethods<T>());
    },
  };
}

Consequently, the @InjectRepository(User) will now inject an instance of Repository<User> with the methods from the BaseRepository interface.

(Please note: the use of the extend method to create a custom repository is recommended since TypeORM 0.3, as mentioned here)

Answer 3

Answer №2

Give this a try, I have successfully implemented this solution in my project

import { Type } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { ObjectLiteral, Repository } from 'typeorm';

interface IDataService<T extends ObjectLiteral> {
  readonly repository: Repository<T>;
  findById: (id: string | number) => Promise<T | null>;
}

type Constructor<I> = new (...args: any[]) => I;

export function MyDataService<T extends ObjectLiteral>(
   entity: Constructor<T>,
): Type<IDataService<T>> {

   class DataServiceHost implements IDataService<T> {
     @InjectRepository(entity) public readonly repository: Repository<T>;

     public async findById(id: string | number): Promise<T | null> {
        return this.repository.findOneBy({ id } as any);
     }
   }
   return DataServiceHost;
}

Extend your service by inheriting from the DataService class,

class YourService extends MyDataService<YourDatabaseEntity>(YourDatabaseEntity)

Answer 4

Give this a try, I have successfully implemented this solution in my project

import { Type } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { ObjectLiteral, Repository } from 'typeorm';

interface IDataService<T extends ObjectLiteral> {
  readonly repository: Repository<T>;
  findById: (id: string | number) => Promise<T | null>;
}

type Constructor<I> = new (...args: any[]) => I;

export function MyDataService<T extends ObjectLiteral>(
   entity: Constructor<T>,
): Type<IDataService<T>> {

   class DataServiceHost implements IDataService<T> {
     @InjectRepository(entity) public readonly repository: Repository<T>;

     public async findById(id: string | number): Promise<T | null> {
        return this.repository.findOneBy({ id } as any);
     }
   }
   return DataServiceHost;
}

Extend your service by inheriting from the DataService class,

class YourService extends MyDataService<YourDatabaseEntity>(YourDatabaseEntity)

Issue with implementing generic inheritance for Repository in NestJS TypeORM: `this.function` is returning an error as it is not

Answer №1

Answer №2

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