> ## Documentation Index
> Fetch the complete documentation index at: https://nestjs-query.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom Service

To create a custom query service to add your own methods to you can extend the `MongooseQueryService`.

```ts title="todo-item.service.ts" theme={null}
import { Model } from 'mongoose'
import { QueryService } from '@ptc-org/nestjs-query-core'
import { InjectModel } from '@nestjs/mongoose'
import { MongooseQueryService } from '@ptc-org/nestjs-query-mongoose'
import { TodoItemEntity } from './entity/todo-item.entity'

@QueryService(TodoItemEntity)
export class TodoItemService extends MongooseQueryService<TodoItemEntity> {

  constructor(@InjectModel(TodoItemEntity.name) model: Model<TodoItemEntity>) {
    super(model)
  }

  async markAllAsCompleted(): Promise<number> {
    const entities = await this.query({ filter: { completed: { is: true } } })

    const { updatedCount } = await this.updateMany(
      { completed: true }, // update
      { id: { in: entities.map((e) => e.id) } } // filter
    )
    // do some other business logic
    return updatedCount
  }
}
```

To use the custom service in the auto-generated resolver you can specify the `ServiceClass` option.

```ts title="todo-item.module.ts" {12,16} theme={null}
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql'
import { NestjsQueryMongooseModule } from '@ptc-org/nestjs-query-mongoose'
import { Module } from '@nestjs/common'
import { TodoItemDTO } from './dto/todo-item.dto'
import { TodoItemEntity } from './todo-item.entity'
import { TodoItemService } from './todo-item.service'

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [
        NestjsQueryMongooseModule.forFeature([
          { document: TodoItemEntity, name: TodoItemEntity.name, schema: TodoItemEntitySchema }
        ])
      ],
      services: [TodoItemService],
      resolvers: [
        {
          DTOClass: TodoItemDTO,
          ServiceClass: TodoItemService
        }
      ]
    })
  ]
})
export class TodoItemModule {}
```