I don’t know what your source is for the claim that you should prefer traits over abstract classes in Scala, but there are several reasons not to: Traits complicate Java compatibility. If you have a trait with a companion object, calling methods on the companion object from Java requires bizarre MyType$.MODULE$.myMethod syntax. This isn’t the … Read more
As a first rule of thumb, I prefer abstract classes over interfaces, based on the .NET Design Guidelines. The reasoning applies much wider than .NET, but is better explained in the book Framework Design Guidelines. The main reasoning behind the preference for abstract base classes is versioning, because you can always add a new virtual … Read more
If you want to check for an overridden instance method in Python 3, you can do this using the type of self: class Base: def __init__(self): if type(self).method == Base.method: print(‘same’) else: print(‘different’) def method(self): print(‘Hello from Base’) class Sub1(Base): def method(self): print(‘Hello from Sub1’) class Sub2(Base): pass Now Base() and Sub2() should both print … Read more
Shouldn’t the inheritance be the other way round? In the MRO foo currently comes before bar_for_foo_mixin, and then rightfully complains. With class myfoo(bar_for_foo_mixin, foo) it should work. And I am not sure if your class design is the right way to do it. Since you use a mixin for implementing bar it might be better … Read more
You can return an abstract class pointer – assuming B is a concrete class derived from abstract class A: A * f() { return new B; } or a reference: A & f() { static B b; return b; } or a smart pointer: std::unique_ptr<A> f() { return std::make_unique<B>(…); }
You’ve declared the destructor, but not defined it. Change the declaration to: virtual ~Force() {} to define it to do nothing. You also want to make all the functions in the abstract interface pure virtual, otherwise they will need to be defined too: virtual VECTOR eval(VECTOR x, double t) = 0;
I’m not sure about Java in particular, but it should be valid. In terms of OOP, if it makes sense, then run with it. To use some old examples, you might have a Vehicle abstract class and then LandVehicle and FlyingVehicle abstract classes. As long as your example makes sense as an abstract class, then … Read more
ref link I just found the answer myself and here is the reference link. What I have done is added some code above the abstract class import com.fasterxml.jackson.annotation.JsonSubTypes; import com.fasterxml.jackson.annotation.JsonTypeInfo; import com.fasterxml.jackson.annotation.JsonTypeInfo.*; @JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = “type”) @JsonSubTypes({ @JsonSubTypes.Type(value = Cat.class, name = “cat”), @JsonSubTypes.Type(value = Dog.class, name = “dog”) }) … Read more
You should go with private constructor. If your class is abstract, it can be extended and objects can be created. As per my understanding from the question, what you want is non instantiable class. from Item 4 of Effective java : Attempting to enforce noninstantiability by making a class abstract does not work. The class … Read more
You’d use an abstract class or interface here in order to make a common base class/interface that provides the void draw() method, e.g. abstract class Shape() { void draw(); } class Circle extends Shape { void draw() { … } } … Shape s = new Circle(); s.draw(); I’d generally use an interface. However you … Read more