Android Room：创建一对一关系实体

我正在创建一个包含房间和三张桌子（作业、标记、类别）的小项目

基本上：

• 作业属于（或具有）1且仅属于类别，但作业可以具有0..N个标记
• 一个类别有0..N个作业
• 标记有0..N个作业

我在尝试对所有数据建模时遇到了一些问题，尤其是在实体之间的关系方面。更具体地说，我有：

fun JobListing.toJobEntityList(): List<JobEntity> {
    val jobEntityList = mutableListOf<JobEntity>()
    this.jobs.take(50).forEach { job: Job ->
        jobEntityList.add(
            JobEntity(
                jobId = job.id,
                title = job.title,
                url = job.url,
                companyName = job.companyName,
                jobType = job.jobType,
                publicationDate = job.publicationDate,
                relocation = job.candidateRequiredLocation,
                salary = job.salary
            )
        )
    }
    return jobEntityList
}

---

提前谢谢

您好，您应该像这样对数据库建模：

工作类别

标签

作业（添加类别\u id字段并添加1个外键引用类别表）

Job_标记（添加标记id、Job_id字段，并添加引用类别和作业表的2个外键）

---

非常感谢你的回答！现在的问题是，对于这个数据库模型，我如何正确地插入从网络中获取的数据？因为现在我的扩展方法

toJobEntityList

希望创建一个

列表

，而每个

JobEntity

都需要一个

categoryId

，我认为我当时没有，你应该先插入类别，然后插入标签，然后再插入作业和标签。如果帖子有帮助，你可以接受它作为答案，那么

jobtag实体的
id
？它不是自动生成的吗？我得到了一个
外键约束失败（代码787 SQLITE\u constraint\u FOREIGNKEY）
当插入该表时，我忘了将其标记为自动生成。但数据来自服务器。如果您的数据模型与此不同，并且没有将标记存储为实体，则可以修改。删除JobTagEntity并使用converter将标记存储为数组
@Entity(
    tableName = "Jobs",
    indices = [
        Index("id", unique = true)
    ]
)
data class JobEntity(
    @PrimaryKey @ColumnInfo(name = "id") val jobId: Int,
    @ColumnInfo(name = "title") val title: String,
    @ColumnInfo(name = "url") val url: String,
    @ColumnInfo(name = "company_name") val companyName: String,
    @ColumnInfo(name = "job_type") val jobType: String,
    @ColumnInfo(name = "publication_date") val publicationDate: String,
    @ColumnInfo(name = "candidate_required_location") val relocation: String,
    @ColumnInfo(name = "salary") val salary: String
)

@Entity(tableName = "Category")
data class CategoryEntity(
    @PrimaryKey @ColumnInfo(name = "id") val id: Int,
)

@Entity(tableName = "Tags")
data class TagEntity(
    @PrimaryKey @ColumnInfo(name = "id") val id: Int,
)

@Entity(
    tableName = "Jobs",
    foreignKeys = [ForeignKey(entity = CategoryEntity::class, parentColumns = ["id"], childColumns = ["categoryid"])]
)
data class JobEntity(
    @PrimaryKey @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "categoryid", index = true) val categoryid: Int,
    // ... other fields
)
@Entity(
    tableName = "JobTags",
    foreignKeys = [
        ForeignKey(entity = TagEntity::class, parentColumns = ["id"], childColumns = ["tagId"]),
        ForeignKey(entity = JobEntity::class, parentColumns = ["id"], childColumns = ["jobId"]),
    ]
)
data class JobTagEntity(
    @PrimaryKey @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "tagId", index = true) val tagId: Int,
    @ColumnInfo(name = "jobId", index = true) val jobId: Int,
)