Room one-to-many, to many-CodePudding

I am little a bit confused on how i should set up a data class consisting of two lists. I have a data class looking like this

@Entity(tableName = "recipe")
data class Recipe(
@PrimaryKey(autoGenerate = false)
val recipeName: String,
//val keyIngrediens: List<KeyIngredient>,
//val steps: List<steps>

So for KeyIngrediens i have set it up like this and it works perfectly without problems

@Entity
data class KeyIngredients(
@PrimaryKey(autoGenerate = false)
val title: String,
val image: String,
val undertitle: Int,
val recipeName: String
)

data class RecipeWithkeyIngredients(
@Embedded val recipe: Recipe,
@Relation(
    parentColumn = "recipeName",
    entityColumn = "recipeName"
)
val keyIngredients: List<KeyIngredients>
)

So basically, i got it to work with one list and one object, but Im a bit confused as how i should handle it when i have two lists in a single object. Right now im calling RecipeWithKeyIngredients which returns the recipe object with the list of key ingredients, but i don't know how to make it also contain the steps list. In short it should be like RecipeWithkeyIngredientsANDsteps if that is possible.

CodePudding user response：

Assuming your Steps data class as follows:

@Entity
data class Steps(
    @PrimaryKay
    val stepName: String,
    val duration: Int,
    val recipeName: String,
    val rank: Int
)

data class RecipeWithKeyIngredientsAndSteps(
    @Embedded recipe: Recipe,
    @Relation(
        parentColumn = "recipeName",
        entityColumn = "recipeName"
    )
    val keyIngredients: List<KeyIngredients>,
    @Relation(
        parentColumn = "recipeName",
        entityColumn = "recipeName"
    )
    val steps: List<Steps>
)

At the end it's still a One-to-N Relationship

CodePudding user response：

This is not enough for recipes. A recipe contains many ingredients, an ingredient belongs to many recipes. So it should be handled with many-to-many relationship.

@Entity
data class Recipe(
  @PrimaryKey
  val id: Long,
  val name: String,
  val steps: List<String>
)

@Entity
data class KeyIngredient(
  @PrimaryKey
  val id: Long,
  val title: String,
  val image: String,
  val undertitle: Int,
)

@Entity(
  primaryKeys = ["recipeId", "keyIngredientId"]
)
data class RecipeKeyIngredient(     
  val recipeId: Long,
  val keyIngredientId: Long
)

Get the list of ingredients

data class IngredientsOfRecipe (
    @Embedded
    val recipe: Recipe,
    @Relation(
            parentColumn = "recipeId",
            entity = KeyIngredient::class,
            entityColumn = "ingredientId",
            associateBy = Junction(
                    value = RecipeKeyIngredient::class,
                    parentColumn = "recipeId",
                    entityColumn = "keyIngredientId"
            )
    )
    val keyIngredients: List<KeyIngredient>
)

Get the list of recipes

data class RecipesWithIngredient(
  @Embedded
  val ingredient: Ingredient,
  @Relation(
        parentColumn = "ingredientId",
        entity = Recipe::class,
        entityColumn = "recipeId",
        associateBy = Junction(
                value = RecipeIngredient::class,
                parentColumn = "ingredientId",
                entityColumn = "recipeId"
        )
  )
  val recipes: List<Recipe>
)

Now you can query database for the result as:

@Dao
interface RecipeKeyIngredientDao {
  @Query("SELECT * FROM Recipe")
  fun getIngredientsOfRecipe(): LiveData<List<IngredientWithRecipes>>

  @Query("SELECT * FROM KeyIngredient")
  fun getRecipesWithIngredient(): LiveData<List<RecipeWithIngredients>>
}

For the other part of the question, a recipe typically contains specific set of steps (instructions?) which belongs to the Recipe table.