About how to use many to one in TypeORM - orm

Question

For the table which has Foreign key, I want to assign ManyToOne's decorator.
I know #ManyToOne(() => User, user => user.photos) is just table relation,
What its argument　() => User, user => user.photos　means?
And please tell me user: User's property and value mean.
import {Entity, PrimaryGeneratedColumn, Column, ManyToOne} from "typeorm";
import {User} from "./User";
#Entity()
export class Photo {
#PrimaryGeneratedColumn()
id: number;
#Column()
url: string;
#ManyToOne(() => User, user => user.photos)
user: User;
}
import {Entity, PrimaryGeneratedColumn, Column, OneToMany} from "typeorm";
import {Photo} from "./Photo";
#Entity()
export class User {
#PrimaryGeneratedColumn()
id: number;
#Column()
name: string;
#OneToMany(() => Photo, photo => photo.user)
photos: Photo[];
}

Answer 1

it just sets the inverse relationship so if you want you could query the other way back. For example:
await this.photoRepository.find({
loadEagerRelations: true,
relations: ['user'],
})
and you would have something like :
[
{
"id": 1,
"url": "https://twetew",
"user": {
"id": 1,
...
...
}
}
]
TypeORM needs this to understand the relation and create the correct reference. In your photos database table it will create a user_id column. User won't have a photo_id.
So:
#ManyToOne(() => User, user => user.photos)
user: User;
creates a user_id column on photos database table and lets you query the other way back.