Android Room - 如何添加 TypeConverter

Question

我目前正在学习 Room Persistence，我只想问一下如何为自定义类创建 TypeConverter？

Brand.kt

@Parcelize
@Entity(tableName = "brand")
data class Brand (
    @PrimaryKey(autoGenerate = false)
    @ColumnInfo(name = "id")
    val id: Int,

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

Product.kt

@Parcelize
@Entity(tableName = "product")
data class Product(
    @PrimaryKey(autoGenerate = false)
    @ColumnInfo(name = "id")
    val id: Int,

    @ColumnInfo(name = "brand")
    val brand: Brand, // This variable is my problem, I don't know how to fix it...

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

    @ColumnInfo(name = "price")
    val price: Int
) : Parcelable

现在我遇到一个错误，它说，

error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.

并指向我的 Product类(class)

我试图在我的 Product 中添加注释类如 @TypeConverters(Brand.class)仍然出现错误，我真的不知道该怎么办。

任何帮助表示赞赏，谢谢。

Answer 1

您可以使用 @Embedded反而。

@Embedded
val brand: Brand,

来自 docs:-

Can be used as an annotation on a field of an Entity or Pojo to signal that nested fields (i.e. fields of the annotated field's class) can be referenced directly in the SQL queries.