如何在房间中存储对象类型

Question

我刚开始在 Android 上使用 Room，遇到了一些困难。我有一个名为“Employee”的类，它具有字符串名称和具有其属性的 Object EmployeeType。我需要在 Room 实体表中表示两者，还需要检查是否存在空值，因为它们可能为空值。

data class Employee(

    @field:SerializedName("name")
    val name: String? = null,

    @field:SerializedName("employee_type")
    val employeeType: EmployeeType? = null,
)

data class EmployeeType(

    @field:SerializedName("full_staff")
    val fullStaff: String? = null,

    @field:SerializedName("contract_staff")
    val contractStaff: String? = null 
)

@Entity
class EmployeeTable (

    @PrimaryKey(autoGenerate = true)
    val id: Int,

    @ColumnInfo(name = "name")
    val name: String

    //.. represent EmployeeType here for both full_staff and contract_staff
    //.. also EmployeeTypes could be null, how do I handle null pointers
)


// My DOA

@Dao
interface EmployeeTableDao {
    @Query("select * from EmployeeTable order by id DESC")
    fun findAll(): LiveData<List<EmployeeTable>>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(employeeTable: List<EmployeeTable>)
}

// API sample

    {
        "staff": [
            {
                "name": "Jeff",
                "employee_type": {
                    "full_staff": "No",
                    "contract_staff": "Yes"
                }
            },
            //...
       ],
    }

请问我该如何实现？

Answer 1

为了将员工数据存储在同一个表中，并稍后在 Kotlin 中访问相同的数据，请在 EmployeeTable 实体类中创建一个 EmployeeType 类型的变量，并创建一个 TypeConvertor 并将其注册到数据库类。 TypeConvertor 将使用 GSON 将 EmployeeType 转换为 JSON 字符串以存储在 DB 中，并在从 DB 访问时返回到 EmployeeType。

@Entity
class EmployeeTable (

    @PrimaryKey(autoGenerate = true)
    val id: Int,

    @ColumnInfo(name = "name")
    val name: String

    @ColumnInfo(name = "employee_type")
    val emmployeeType: EmployeeType
)

---

转换器类

class EmployeeTypeConvertor {

    @TypeConverter
    fun fromEmployeeType(employeeType: EmployeeType): String {
        return /* JSON string using GSON or something */
    }

    @TypeConverter
    fun toEmployeeType(employeeType: String): EmployeeType {
        return /* EmployeeType from JSON string using GSON or something */
    }
}