Decorators

NestJS CRUD Automator is built on a powerful decorator system that enables declarative API development. Decorators are the primary interface for configuring entity properties, services, controllers, and subscribers.

Decorator Categories

Controller Decorators

`@ApiController`

The main decorator for automatically generating CRUD controllers. Applied to controller classes to enable automatic endpoint generation.

post.controller.ts


import { Controller } from "@nestjs/common";
import { ApiController, EApiRouteType } from "@elsikora/nestjs-crud-automator";
import { PostEntity } from "./post.entity";
import { PostService } from "./post.service";
 
@Controller("posts")
@ApiController<PostEntity>({
  entity: PostEntity,
  name: "Posts",
  routes: {
    [EApiRouteType.CREATE]: {},
    [EApiRouteType.GET]: {},
    [EApiRouteType.GET_LIST]: {},
    [EApiRouteType.UPDATE]: {},
    [EApiRouteType.DELETE]: {},
  },
})
export class PostController {
  constructor(public service: PostService) {}
}

`@ApiControllerObservable`

Marks a controller as observable, enabling the subscriber system to intercept its operations. Required when using route-level subscribers.

post.controller.ts


import { Controller } from "@nestjs/common";
import {
  ApiController,
  ApiControllerObservable
} from "@elsikora/nestjs-crud-automator";
 
@Controller("posts")
@ApiController({ /* ... */ })
@ApiControllerObservable()
export class PostController {
  constructor(public service: PostService) {}
}

Service Decorators

`@ApiService`

Automatically adds CRUD methods to service classes. The service must extend ApiServiceBase and provide a repository.

post.service.ts


import { Injectable } from "@nestjs/common";
import { InjectRepository } from "@nestjs/typeorm";
import { Repository } from "typeorm";
import { ApiService, ApiServiceBase } from "@elsikora/nestjs-crud-automator";
import { PostEntity } from "./post.entity";
 
@Injectable()
@ApiService<PostEntity>({
  entity: PostEntity,
})
export class PostService extends ApiServiceBase<PostEntity> {
  constructor(
    @InjectRepository(PostEntity)
    public repository: Repository<PostEntity>,
  ) {
    super();
  }
}

`@ApiServiceObservable`

Marks a service as observable, enabling function-level subscribers to intercept repository operations.

post.service.ts


import { Injectable } from "@nestjs/common";
import {
  ApiService,
  ApiServiceBase,
  ApiServiceObservable
} from "@elsikora/nestjs-crud-automator";
 
@Injectable()
@ApiService({ /* ... */ })
@ApiServiceObservable()
export class PostService extends ApiServiceBase<PostEntity> {
  // ...
}

Property Decorators

`@ApiPropertyDescribe`

The fundamental decorator for entity properties. Provides metadata used for DTO generation, validation, and Swagger documentation.

user.entity.ts


import { Entity, PrimaryGeneratedColumn, Column } from "typeorm";
import {
  ApiPropertyDescribe,
  EApiPropertyDescribeType,
  EApiPropertyStringType
} from "@elsikora/nestjs-crud-automator";
 
@Entity("users")
export class UserEntity {
  @PrimaryGeneratedColumn("uuid")
  @ApiPropertyDescribe({
    type: EApiPropertyDescribeType.UUID,
    description: "User unique identifier",
  })
  id: string;
 
  @Column()
  @ApiPropertyDescribe({
    type: EApiPropertyDescribeType.STRING,
    description: "User name",
    format: EApiPropertyStringType.STRING,
    minLength: 3,
    maxLength: 50,
    exampleValue: "john_doe",
  })
  username: string;
}

Supported property types:

UUID - Unique identifiers
STRING - Text fields with validation rules
NUMBER - Numeric fields with range validation
BOOLEAN - Boolean flags
DATE - Date and timestamp fields
ENUM - Enumeration types
OBJECT - Nested objects with discriminator support
RELATION - Entity relations

Subscriber Decorators

`@ApiRouteSubscriber`

Creates a route-level subscriber that intercepts controller operations. Provides access to HTTP context (headers, IP, authenticated user).

post-audit.subscriber.ts


import { Injectable } from "@nestjs/common";
import {
  ApiRouteSubscriber,
  ApiRouteSubscriberBase,
  IApiSubscriberRouteExecutionContext
} from "@elsikora/nestjs-crud-automator";
import { PostEntity } from "./post.entity";
 
@Injectable()
@ApiRouteSubscriber({
  entity: PostEntity,
  priority: 10
})
export class PostAuditSubscriber extends ApiRouteSubscriberBase<PostEntity> {
  async onAfterCreate(
    context: IApiSubscriberRouteExecutionContext<PostEntity, PostEntity>
  ): Promise<PostEntity> {
    console.log("Post created:", context.result);
    return context.result;
  }
}

`@ApiFunctionSubscriber`

Creates a function-level subscriber that intercepts service operations. Operates at the database layer before and after repository methods.

post-slug.subscriber.ts


import { Injectable } from "@nestjs/common";
import {
  ApiFunctionSubscriber,
  ApiFunctionSubscriberBase,
  IApiSubscriberFunctionExecutionContext,
  TApiFunctionCreateProperties
} from "@elsikora/nestjs-crud-automator";
import { PostEntity } from "./post.entity";
 
@Injectable()
@ApiFunctionSubscriber({
  entity: PostEntity
})
export class PostSlugSubscriber extends ApiFunctionSubscriberBase<PostEntity> {
  async onBeforeCreate(
    context: IApiSubscriberFunctionExecutionContext<PostEntity, TApiFunctionCreateProperties<PostEntity>>
  ): Promise<TApiFunctionCreateProperties<PostEntity>> {
    // Modify data before saving
    return context.result;
  }
}

Decorator Composition

Decorators can be combined to create sophisticated configurations:

product.controller.ts


@Controller("products")
@ApiController<ProductEntity>({
  entity: ProductEntity,
  name: "Products",
  routes: {
    [EApiRouteType.CREATE]: {
      authentication: {
        guard: JwtAuthGuard,
        bearerStrategies: ["jwt"],
      },
      autoDto: {
        [EApiDtoType.BODY]: {
          validators: [
            {
              constraintClass: AllOrNoneOfListedPropertiesValidator,
              options: ["price", "discountPrice"],
            },
          ],
        },
      },
    },
  },
})
@ApiControllerObservable()
export class ProductController {
  constructor(public service: ProductService) {}
}

Next Steps

Entities - Configure entity properties
Controllers - Controller configuration
Services - Service layer setup
Subscriber System - Intercept operations with hooks