I have a Brand class that has several products
And in the product class I want to have a reference to the brand, like this:
case class Brand(val name:String, val products: List[Product])
case class Product(val name: String, val brand: Brand)
How can I poulate these classes???
I mean, I can't create a product unless I have a brand
And I can't create the brand unless I have a list of Products (because Brand.products is a val)
What would be the best way to model this kind of relation?
I would question why you are repeating the information, by saying which products relate to which brand in both the List and in each Product.
Still, you can do it:
class Brand(val name: String, ps: => List[Product]) {
lazy val products = ps
override def toString = "Brand("+name+", "+products+")"
}
class Product(val name: String, b: => Brand) {
lazy val brand = b
override def toString = "Product("+name+", "+brand.name+")"
}
lazy val p1: Product = new Product("fish", birdseye)
lazy val p2: Product = new Product("peas", birdseye)
lazy val birdseye = new Brand("BirdsEye", List(p1, p2))
println(birdseye)
//Brand(BirdsEye, List(Product(fish, BirdsEye), Product(peas, BirdsEye)))
By-name params don't seem to be allowed for case classes unfortunately.
See also this similar question: Instantiating immutable paired objects
Since your question is about model to this relationship, I will say why not just model them like what we do in database? Separate the entity and the relationship.
val productsOfBrand: Map[Brand, List[Product]] = {
// Initial your brand to products mapping here, using var
// or mutable map to construct the relation is fine, since
// it is limit to this scope, and transparent to the outside
// world
}
case class Brand(val name:String){
def products = productsOfBrand.get(this).getOrElse(Nil)
}
case class Product(val name: String, val brand: Brand) // If you really need that brand reference
Related
I have a list of data object that looks as follows:
data class Detail (
val type1: Type1
val type2: Type2
)
val list: List<Detail> = arrayListOf(Detail,Detail,Detail)
How do I bind the the list of details into a JDBI SQL query. I know how to do it with a single data type but just not sure how this works when you are getting properties from the "Detail" data class.
eg:
it.createQuery(
"""
SELECT
id
FROM
tbl_of_something
WHERE
type1
AND
type2
IN (<detail>)
"""
).bindList("detail", list)
.mapTo(String::class.java)
.toSet()
.toList()
.sorted()
I figured it out, this can be solved by using bindBeanList() as follows:
it.createQuery(
"""
SELECT
id
FROM
tbl_of_something
WHERE
(type1, type2)
IN (<detail>)
"""
).bindBeanList("detail", list, listOf("type1", "type2"))
.mapTo(String::class.java)
.toSet()
.toList()
.sorted()```
I have to sort list of object by lastName and firstName (if case there is the same lastName for multiple objects). I must also apply Collator to those.
Suppose I can do that for one property:
val collator = Collator.getInstance(context.getResources().getConfiguration().locale)
myList.sortedWith(compareBy(collator, { it.lastName.toLowerCase() }))
But is it possible to apply also to that another restriction to also sort by firstName?
You can add another sort criteria with thenBy:
val comparator =
compareBy(collator) { p: Person -> p.lastName.toLowerCase() }
.thenBy(collator) { p: Person -> p.firstName.toLowerCase() }
val result = myList.sortedWith(comparator)
Simplest would just be to concatenate the two properties in the selector lambda:
myList.sortedWith(
compareBy(collator) { "${it.lastName} ${it.firstName}".toLowerCase() }
)
I have a model structure as following:
Group -> Many Parties -> Many Participants
In on of the API calls I need to get single groups with parties and it's participants attached.
This whole structure is built on 4 tables:
group
party
party_participant
participant
Naturally, with SQL it's a pretty straight forward join that combines all of them. And this is exactly what I am trying to do with slick.
Mu method is dao class looks something like this:
def findOneByKeyAndAccountIdWithPartiesAndParticipants(key: UUID, accountId: Int): Future[Option[JourneyGroup]] = {
val joins = JourneyGroups.groups join
Parties.parties on (_.id === _.journeyGroupId) joinLeft
PartiesParticipants.relations on (_._2.id === _.partyId) joinLeft
Participants.participants on (_._2.map(_.participantId) === _.id)
val query = joins.filter(_._1._1._1.accountId === accountId).filter(_._1._1._1.key === key)
val q = for {
(((journeyGroup, party), partyParticipant), participant) <- query
} yield (journeyGroup, party, participant)
val result = db.run(q.result)
result ????
}
The problem here, is that the result is type of Future[Seq[(JourneyGroup, Party, Participant)]]
However, what I really need is Future[Option[JourneyGroup]]
Note: case classes of JourneyGroup and Party have sequences for there children defined:
case class Party(id: Option[Int] = None,
partyType: Parties.Type.Value,
journeyGroupId: Int,
accountId: Int,
participants: Seq[Participant] = Seq.empty[Participant])
and
case class JourneyGroup(id: Option[Int] = None,
key: UUID,
name: String,
data: Option[JsValue],
accountId: Int,
parties: Seq[Party] = Seq.empty[Party])
So they both can hold the descendants.
What is the correct way to convert to the result I need? Or am I completely in a wrong direction?
Also, is this statement is correct:
Participants.participants on (_._2.map(_.participantId) === _.id) ?
I ended up doing something like this:
journeyGroupDao.findOneByKeyAndAccountIdWithPartiesAndParticipants(key, account.id.get) map { data =>
val groupedByJourneyGroup = data.groupBy(_._1)
groupedByJourneyGroup.map { case (group, rows) =>
val parties = rows.map(_._2).distinct map { party =>
val participants = rows.filter(r => r._2.id == party.id).flatMap(_._3)
party.copy(participants = participants)
}
group.copy(parties = parties)
}.headOption
}
where DAO method's signature is:
def findOneByKeyAndAccountIdWithPartiesAndParticipants(key: UUID, accountId: Int): Future[Seq[(JourneyGroup, Party, Option[Participant])]]
Given tables of:
case class Person(id: Int, name: String)
case class Dead(personId: Int)
and populated with:
Person(1, "George")
Person(2, "Barack")
Dead(1)
is it possible to have a single query that would produce a list of (Person, Option[Dead]) like so?
(Person(1, "George"), Some(Dead(1)))
(Person(2, "Barack"), None)
For slick 3.0 it should be something like this:
val query = for {
(p, d) <- persons joinLeft deads on (_.id === _.personId)
} yield (p, d)
val results: Future[Seq[(Person, Option[Dead])]] = db.run(query.result)
In slick, outer joins are automatically wrapped in an Option type. You can read more about joining here: http://slick.typesafe.com/doc/3.0.0/queries.html#joining-and-zipping
Imagine I have two classes in Groovy that look like that:
class Person {
int id;
String name;
}
class Item {
int id;
int price;
}
Now it would be simple to create a JasperReport listing all persons' names using the following SQL:
SELECT name FROM Person
Also, it would be easy to pass a Model from which the list should be created:
def p = Person.withCriteria {
eq('name','SomeGuy')
}
chain(controller:'jasper',action:'index',model:[data:p],params:params)
But what I want to do is to use the following query:
SELECT name, (SELECT sum(i.price) FROM Item f WHERE f.id=p.id) as priceSum FROM Person p
And now this is the part where I don't know how to go on: How can I pass any Model to the jasperReport? I can't just use
def p = Person.withCriteria {
eq('name','SomeGuy')
}
because then, the priceSum attribute would be missing.
What I would like to do is something like this:
def l = ['name':'SomeGuy','priceSum':'5000']
chain(controller:'jasper',action:'index',model:[data:l],params:params)
But this doesn't work either, it gives me:
Message: Cannot get property 'name' on null object
Caused by: java.lang.NullPointerException: Cannot get property 'name' on null object
Is there anything simliar to this that would work?