Kotlin Nullable Any

Question

I am new to Kotlin. I am facing the following problem. I have a function like this,

fun updateAfterFind(updateColumn:Map<Column<*>, Any?>): Boolean{
    ExposedUser.update( {ExposedUser.id eq 123} ){
        for (column in updateColumn){
            it[column.key] = column.value
        }
    }
    return true;
}

The column.value is of type Any?. Still I am getting the following error,

I have also tried casting, column.name as Any?. But it didn't helped.

After doing gradle build I got the following error,

Type inference failed: Cannot infer type parameter S in fun <S> set(column: Column<S>, value: S?): Unit
None of the following substitutions
(Column<CapturedTypeConstructor(*)>,CapturedTypeConstructor(*)?)
(Column<Any>,Any?)
can be applied to
(Column<*>,Any)

@MattTimmermans `fun T.update(where: SqlExpressionBuilder.()->Op, limit: Int? = null, body: T.(UpdateStatement)->Unit): Int` — BhaskerYadav, Nov 28 '19 at 04:04
@smac89 `it` is of type `ExposedUser` which extends `org.jetbrains.exposed.sql.Table` — BhaskerYadav, Nov 28 '19 at 04:13

Matt Timmermans · Accepted Answer · 2019-11-28T04:31:27.657

The signature for <S> UpdateStatement.set(Column<S>,S?) says that the type parameter for the column has to match the value type.

You have a Column<*> and a value Any. That doesn't match, because Column<*> is not the same as Column<Any>. The * could be anything, so it could be a Column<Integer>, for example, and you can't set an Any as the value.

If you know that the types really are compatible, then you can override the check by saying it[column.key as Column<Any>] = column.value

The cast is gross, but using that Map to store these updates is not type-safe, and this is where you have to take responsibility for that.

Kotlin Nullable Any

1 Answers1