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api-docs / org.ktorm.schema / SqlType / transform


open fun <R : Any> transform(
    fromUnderlyingValue: (T) -> R,
    toUnderlyingValue: (R) -> T
): SqlType<R>
(source code)

Transform this SqlType to another. The returned SqlType has the same typeCode and typeName as the
underlying one, and performs the specific transformations on column values.

This function enables a user-friendly syntax to extend more data types. For example, the following code defines
a column of type Column<UserRole>, based on the existing IntSqlType:

val role by registerColumn("role", IntSqlType.transform({ UserRole.fromCode(it) }, { it.code }))


fromUnderlyingValue - a function that transforms a value of underlying type to the user’s type.

toUnderlyingValue - a function that transforms a value of user’s type to the underlying type.

a SqlType instance based on this underlying type with specific transformations.