Object members switch

When using metamodel, for object information extraction, like member attributes or member functions. It would be nice to have possibility to switch over this extracted values.

For example I would like to create mapping between two representation of the same domain model, a DTO and database model, for some reason names of attributes does not match.

class PersonDb(Integer id,shared String personName,shared Integer personAge){}
class PersonDto(shared String name,shared Integer age ){}

Currently the simplest form of mapping between those two attributes I can make, look like:

Attribute<PersonDto>? mapAttributes(Attribute<PersonDb> dbAttribute) =>
	if(dbAttribute==`PersonDb.personAge`) then `PersonDto.age` 
	else if(dbAttribute==`PersonDb.personName`) then `PersonDto.name`
	else null;

And it would be nice to have something like this:

Attribute<PersonDto>? mapSwitchAttributes(Attribute<PersonDb> dbAttribute) =>
	switch(dbAttribute)
	case(is `PersonDb.personAge`){
	    return `PersonDto.age`;
	}
	case(is `PersonDb.personName`){
	    return `PersonDto.name`;
	}else{
	    return null;
	}

Of course with exhausting requirement “Case types must cover all cases of the switch type or an else clause must appear”

[gavinking]

No, it’s not possible today, but in principle it would be pretty simple to add.

[xkr47]

Some ideas…

• use a map somehow:

value memberMap = map {
  `PersonDb.personAge` -> `PersonDto.age`,
  `PersonDb.personName` -> `PersonDto.name`
};

• use annotations on members in either PersonDb or PersonDto like:

class PersonDb(
  Integer id,
  mapToDto(`PersonDto.name`) shared String personName,
  mapToDto(`PersonDto.age`) shared Integer personAge
){}