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Scala "multilevel" abstract class / abstract objects replacement


Scala "multilevel" abstract class / abstract objects replacement

By : RW Beman
Date : November 15 2020, 06:54 AM
like below fixes the issue I don't think abstract classes are necessary here since it seems like you just want an immutable data structure without any actual inheritance. Nested case classes should do just fine.
code :
case class Settings(server: ObjectServer, connectionPools: ConnectionPools)
case class ObjectServer(URL: String, timeout: Int)
case class ConnectionPools(limits: Limits)
case class Limits(timeout: Int, max: Int, prefix: String)

val settings = Settings(
    ObjectServer(
        URL = "http://localhost:8081",
        timeout = 20
    ),
    ConnectionPools(
        Limits(
            timeout = 10,
            max = 5,
            prefix = "pref_"
        )
    )
)
abstract class Settings {
    val server: ObjectServer
    val connectionPools: ConnectionPools
}

abstract class ObjectServer {
    val URL: String
    val timeout: Int
}

abstract class ConnectionPools {
    val limits: Limits
}

abstract class Limits {
    val timeout: Int
    val max: Int
    val prefix: String
}

object MySettings extends Settings {
    val server = new ObjectServer {
       val URL = "http://localhost:8081"
       val timeout = 20
    }

    val connectionPools = new ConnectionPools {
        val limits = new Limits {
            val timeout = 10
            val max = 5
            val prefix = "pref_"
        }
    }
 }


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Android Activity with Abstract Base Class throws a compile error "is not abstract and does not overrid abstract met

Android Activity with Abstract Base Class throws a compile error "is not abstract and does not overrid abstract met


By : Orlando Morales
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , if you extend an Abstract Class you need to make the method either abstract in extended class or you need to provide implementations:
code :
public abstract class BaseCategoryListActivity extends ListActivity
{
    ....
    public abstract ArrayList<String> getListItems();
    ....
}

public class AthleticsNewsActivity extends BaseCategoryListActivity
{
    ....
    public ArrayList<String> getListItems()
    {
       ...implementation details....
    }
}
Django automatically inheriting "abstract = true" from an abstract meta class

Django automatically inheriting "abstract = true" from an abstract meta class


By : user3241448
Date : March 29 2020, 07:55 AM
Hope that helps Your CommonFunctions should be based on models.Model, not object. This way, you will get the behavior stated in the Django documentation.
code :
class CommonFunctions(models.Model):

    def get_absolute_url(self):
        return "/{0}/list/".format(self.__class__.__name__).lower()

    def get_fields(self):
        return [(field, field.value_to_string(self)) for field in   (self.__class__)._meta.fields]

    class Meta:
          abstract = True
class Book(CommonFunctions):
    book_name = models.CharField(max_length=30)
    book_area = models.CharField(max_length=30)
Abstract class with pure virtual method - why is it possible to do "Abstract * abs3;"?

Abstract class with pure virtual method - why is it possible to do "Abstract * abs3;"?


By : Ashish
Date : March 29 2020, 07:55 AM
should help you out abs3 is a pointer to the class. It can be initialized to any concrete subclass of Abstract, or to NULL, safely. The compiler has to allow it because while you can't create abstract classes, you have to be able to create pointers to them. See below for an example
code :
class Concrete: public Abstract
{
public:
    virtual void func() { // do something };
};


int main ()
{
   Abstract* abs3 = NULL;
   abs3 = new Concrete;
}
Keep getting error "(CLASS) is not abstract and does not override abstract method"

Keep getting error "(CLASS) is not abstract and does not override abstract method"


By : Ian D. Fantini
Date : March 29 2020, 07:55 AM
Does that help The method name should be actionPerformedand not actionPerfomed. You missed a r
Can an F# abstract class type member expression be "abstract override"?

Can an F# abstract class type member expression be "abstract override"?


By : Arnold
Date : March 29 2020, 07:55 AM
will help you You can declare a method abstract override in a C# abstract class. You might do this to force a derived type to provide an implementation of a base method of System.Object, like ToString(). It looks like this in C#: , The F# specification says the following about abstract members:
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