Monto Type Hierarchy Question

[AGYNAMIX Torsten Uhlmann]

Hi,

I have a question on extending MongoMetaRecord or more specifically, an error I get while doing so and I can not figure out what's the problem.

I try to create a trait:

trait StructuredDbObject[BaseRecord <: MongoRecord[BaseRecord]] 

      extends MongoMetaRecord[BaseRecord]

This gives me the compiler error:

illegal inheritance;  self-type StructuredDbObject[BaseRecord] does not conform to net.liftweb.mongodb.record.MongoMetaRecord[BaseRecord]'s selftype net.liftweb.mongodb.record.MongoMetaRecord[BaseRecord] with BaseRecord

Looking at the MongoMetaRecord definition it has the same type definition as above:

trait MongoMetaRecord[BaseRecord <: MongoRecord[BaseRecord]]

Can you point me to the mistake I'm making, please?

Thanks,

Torsten.

[Tobias Pfeiffer]

Hi Torsten,

Am Dienstag, 16. Oktober 2012, 18:52 schrieb AGYNAMIX Torsten Uhlmann:
> I try to create a trait:
>
> trait StructuredDbObject[BaseRecord <: MongoRecord[BaseRecord]]
> extends MongoMetaRecord[BaseRecord]
>
> This gives me the compiler error:
>
> illegal inheritance; self-type StructuredDbObject[BaseRecord] does
> not conform to
> net.liftweb.mongodb.record.MongoMetaRecord[BaseRecord]'s selftype
> net.liftweb.mongodb.record.MongoMetaRecord[BaseRecord] with
> BaseRecord
>
> Looking at the MongoMetaRecord definition it has the same type
> definition as above:
>
> trait MongoMetaRecord[BaseRecord <: MongoRecord[BaseRecord]]

However, MongoMetaRecord's Self type is
MongoMetaRecord[BaseRecord] with BaseRecord
see <http://scala-
tools.org/mvnsites/liftweb-2.4/#net.liftweb.mongodb.record.MongoMetaRecord>
and <http://www.scala-lang.org/node/124>

So maybe try to add a self type as well or write

trait StructuredDbObject[BaseRecord <: MongoRecord[BaseRecord]]

extends BaseRecord with MongoMetaRecord[BaseRecord]
or something?

Tobias

[AGYNAMIX Torsten Uhlmann]

Thanks, Tobias, for your help!

It turns out I really just missed declaring the self type:

trait StructuredDbObject[BaseRecord <: MongoRecord[BaseRecord]] 

      extends MongoMetaRecord[BaseRecord] {

  self: BaseRecord =>

  ...

}

Adding that "self" declaration does miracles to the compiler :)

Thanks,

Torsten.

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