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@JoinColumn
- 在一对一关系中，@JoinColumn 只需要加到其中一张表的字段上. 比如PhotoMetadata和Photo是一对一， 如果2张表都加了@JoinColumn只会在其中一张表增加一个外键字段 photoId 或者 metadataId
@Entity()
export class PhotoMetadata {
@PrimaryGeneratedColumn()
id: number
@Column("int")
height: number
@Column("int")
width: number
@Column()
orientation: string
@Column()
compressed: boolean
@Column()
comment: string
@OneToOne(() => Photo, (photo)=> photo.metadata )
@JoinColumn()
photo: Photo
}
@Entity()
export class Photo {
@PrimaryGeneratedColumn()
id: number
@Column({
length: 100,
})
name: string
@Column("text")
description: string
@Column()
filename: string
@Column("double")
views: number
@Column()
isPublished: boolean
// @JoinColumn() 不用加这个，因为PhotoMetadata 已经有了JoinColumn了
@OneToOne(()=> PhotoMetadata, (photoMetadata)=> photoMetadata.photo)
metadata: PhotoMetadata
}
cascade 表示保存实体类型时，也把关联的实体保存
@Entity()
export class Photo {
@PrimaryGeneratedColumn()
id: number
@Column({
length: 100,
})
name: string
// @JoinColumn()
@OneToOne(()=> PhotoMetadata, (photoMetadata)=> photoMetadata.photo,{
cascade: true
})
metadata: PhotoMetadata
}
// create a photo
const photo = new Photo()
photo.name = "6beautiful"
photo.isPublished = true
// create a photo metadata
const metadata = new PhotoMetadata()
metadata.orientation = "portrait"
metadata.photo = photo // this way we connect them
photo.metadata = metadata;
const photoRepository = AppDataSource.getRepository(Photo)
await photoRepository.save(photo); // 因为photo的metadata字段有cascade, 因此保存photo,也会把metadata一起save，
// 下面不用再写
// const metadataRepository = AppDataSource.getRepository(PhotoMetadata)
// await metadataRepository.save(metadata)