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Version: 5.5

Using Entity Constructors

Internally, MikroORM never calls entity constructor, so you are free to use it as you wish. The constructor will be called only when you instantiate the class yourself via new operator, so it is a handy place to require your data when creating new entity.

For example following Book entity definition will always require to set title and author, but publisher will be optional:

export class Book {

id!: number;

title!: string;

author!: Author;

publisher?: Publisher;

@ManyToMany({ entity: () => BookTag, inversedBy: 'books' })
tags = new Collection<BookTag>(this);

constructor(title: string, author: Author) {
this.title = title; = author;


Using native private properties

If we want to use native private properties inside entities, the default approach of how MikroORM creates entity instances via Object.create() is not viable (more about this in the issue). To force usage of entity constructors, we can use forceEntityConstructor toggle.