Multiple Sources

The standard Mappie ObjectMappie base class maps a single source parameter to a single target parameter. Mappie also supports mapping multiple source parameters to a single target parameter.

Mappie supports up to five source parameters. This can be achieved via the base classes ObjectMappie2, ObjectMappie3, ..., ObjectMappie5.

For example, suppose we want to map the sources Person, Address, and ContactInformation to PersonDto. We can write this as

object PersonDtoMapper : ObjectMappie3<Person, Address, ContactInformation, PersonDto>() {
    override fun mapping(first: Person, second: Address, third: ContactInformation): PersonDto = mapping {
        // mapping logic
    }
}

When multiple source parameters are used, and there are multiple properties with the same name in these source parameters, Mappie will not construct an implicit mapping using either of those properties. This would be an arbitrary choice, and not transparent.

Note that these multiple source mappers have less built-in functionality, most notable mapping lists and sets as described in List & Sets.