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junior
Asked: 2022-08-03 07:33:40 +0800 CST 2022-08-03 07:33:40 +0800 CST

How to do an upsert with Room in kotlin?

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I already investigated in English I get this option android-room-persistence-library-upsert I modified it a bit and I stay like this:

    @Dao
    interface BloqueDao {
        @Query("SELECT * FROM bloque")
        suspend fun getAll(): List<bloque>

        @Query("UPDATE bloque SET act=1 WHERE idfin=:finc")
        suspend fun prevSetUp(finc : Int)

        @Insert( onConflict = OnConflictStrategy.IGNORE)
        suspend fun insertAll(vararg bloques: bloque?)

        @Update
        suspend fun update(vararg bloques: bloque?)

        @Delete
        suspend fun delete(blo: bloque)

        @Transaction
        suspend fun upsert(vararg bloques: bloque?) {
            val insertResult = insertAll(*bloques)
            if(insertResult is List<Long>){
                val updateList: MutableList<bloque?> = ArrayList()
                for (i in insertResult.indices)
                    if (insertResult[i] == -1L)
                        updateList.add(bloques[i])
                if (updateList.isNotEmpty())
                    update(*updateList.toTypedArray())
            }else if (insertResult == -1L)
                update(bloques[0])

        }
    }

the problem is that kotlin tells me Incompatible types: List<Long>and Unit. but the room library documentation says:

If the @Insert method receives only 1 parameter, it can return a long, which is the new rowId for the inserted element. If the parameter is an array or a collection, it should return long[] or List

I get this error before compiling it, if I tell it that the function insertAll returns AnyI get another error but in debugging

bug image

enter image description here

bug description

Cannot check for instance of erased type: List. Incompatible types: List and Unit.

SOLUTION

functions must be created separately

    @Dao
    interface BloqueDao {
        @Query("SELECT * FROM bloque")
        suspend fun getAll(): List<bloque>

        @Query("UPDATE bloque SET act=1 WHERE idfin=:finc")
        suspend fun prevSetUp(finc : Int)

        @Insert(onConflict = OnConflictStrategy.IGNORE)
        suspend fun insert(bloq: bloque) : Long

        @Insert(onConflict = OnConflictStrategy.IGNORE)
        suspend fun insertAll(bloques: List<bloque>) : List<Long>
        @Update
        suspend fun update(vararg bloques: bloque)

        @Delete
        suspend fun delete(blo: bloque)

        @Transaction
        suspend fun upsert(bloq: bloque) = insert(bloq).takeIf { it == -1L }.run { update(bloq) }

        @Transaction
        suspend fun upsert(bloques: List<bloque>) = insertAll(bloques)
        .withIndex()
        .filter { it.value == -1L }
        .map { bloques[it.index] }
        .let { if (it.isNotEmpty()) update(*it.toTypedArray()) }
    }
android

1 Answers

  1. Best Answer

    Read the documentation carefully

    If the method @Insertreceives only 1 parameter, it can return a long, which is the new one rowIdfor the inserted element. If the parameter is an array or a collection, it should return long[]or List<Long>.

    The key word is " can ". This means that if you want , you can make it return a Long. But you defined your function insertAlllike this

    suspend fun insertAll(vararg bloques: bloque?)

    In Kotlin if you don't specify the return type of a function, it is considered to be Unit. In other words, for one to return, List<Long>you must specify it explicitly.

    suspend fun insertAll(vararg bloques: bloque?): List<Long>

    Although there are some things you should keep in mind. By convention, class names must start with a capital letter. That is, it should not be called bloquebut Bloque. It also shouldn't be nullable because it doesn't work with null values. And the use of varargis also not highly recommended in this case. I assume you use it for the same function to insert one or more elements but this can be confusing. It is preferable to split it at inserte insertAll. This way you separate the responsibilities and get the name to correctly describe the behavior of the function.

    Following good practices it should look like this

    suspend fun insertAll(bloques: List<Bloque>): List<Long>

    But none of this is necessary because Room already has an implementation of " upsert ". You just have to use the annotation @Insertwith the argument OnConflictStrategy.REPLACE

    @Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun upsert(bloques: List<Bloque>)

    If you want to write your own implementation anyway, you should replace that code (which looks like an automatic conversion from Java to Kotlin) with something more idiomatic. This is exactly the same as you had but using kotlin properly

    @Transaction
suspend fun upsert(bloques: List<Bloque>) = insertAll(bloques)
    .withIndex()
    .filter { it.value == -1L }
    .map { bloques[it.index] }
    .let { if (it.isNotEmpty()) updateAll(it) }
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