MikroORM Entity Guide

Use this skill when creating or modifying MikroORM entity files (*.entity.ts).

Basic Entity Structure

import { Entity, PrimaryKey, Property, Unique } from '@mikro-orm/core';
import { uuidv7 } from 'uuidv7';

import { EntityEnum } from '../entity.enums';

@Entity()
export class EntityName {
  @PrimaryKey({ type: 'uuid' })
  id: string = uuidv7();

  @Property()
  @Unique()
  uniqueField!: string;

  @Property({ length: 30, nullable: true })
  optionalField?: string;

  @Property({ type: 'date', nullable: true })
  dateField?: Date;

  @Property({ type: 'string', nullable: true })
  enumField?: EntityEnum;

  @Property({ onCreate: () => new Date() })
  createdAt?: Date;

  @Property({ onCreate: () => new Date(), onUpdate: () => new Date() })
  updatedAt?: Date;
}

Core Rules

1. Primary Key

• •Use UUID v7: Use uuidv7 package for time-ordered UUIDs
• •Assign default value directly in class field (= uuidv7())

2. Property Decorators

• •Required fields: Use ! (definite assignment assertion)
• •Optional fields: Use ? (optional) with nullable: true option
• •String length limits: Use length option
• •Date type: Explicitly specify { type: 'date' }

3. Enum Fields

• •Use @Property({ type: 'string' })
• •Define enums in separate .enums.ts file

4. Timestamps

• •onCreate: Auto-set on creation
• •onUpdate: Auto-update on modification
• •Both fields declared as optional (?)

5. Unique Constraints

• •Place @Unique() decorator below @Property()

Enum File Structure (*.enums.ts)

export enum EntityStatus {
  ACTIVE = 'ACTIVE',
  INACTIVE = 'INACTIVE',
  DELETED = 'DELETED',
}

export enum EntityType {
  TYPE_A = 'TYPE_A',
  TYPE_B = 'TYPE_B',
}

• •Values in uppercase SNAKE_CASE
• •Keep key and value identical

File Naming Conventions

• •Entity file: {entity-name}.entity.ts
• •Enum file: {module-name}.enums.ts
• •Folder structure: src/{module}/entities/