abstract-methods

Okay so basically I have the following problem: I'm trying to have an abstract class inherit another abstract class that has an abstract method, but I don't want to implement the abstract method in either of them because a third class inherits from both of them: public abstract class Command { public abstract object execute(); } public abstract class Binary : Command { public abstract object execute(); //the issue is here } public class Multiply : Binary { public override object execute() { //do stuff } } I'm trying to separate binary commands from unary commands but don't want to/can't

This question already has an answer here : What should I put in the body of an abstract method in Python (1 answer) I have an abstract class, Model , with a few abstract methods, what should I put in the body of the methods? A return class Model(metaclass=ABCMeta): @abstractmethod def foo(self): return A pass class Model(metaclass=ABCMeta): @abstractmethod def foo(self): pass Raising a descriptive error class Model(metaclass=ABCMeta): @abstractmethod def foo(self): raise NotImplementedError("Class {class_name} doesn't implement {func_name} function" .format(class_name=self.__class__.__name__,

Is it necessary for an abstract class to have at least one abstract method? The subject of this post and the body ask two different questions: Should it have at least one abstract member? Is it necessary to have at least one abstract member? The answer to #2 is definitively no. The answer to #1 is subjective and a matter of style. Personally I would say yes. If your intent is to prevent a class (with no abstract methods) from being instantiated, the best way to handle this is with a private protected constructor, not by marking it abstract . No, it is not necessary. You see this often back in

I am trying to design one Abstract class and method in Android and call those methods by extending the class from my parent Activity class but i don't how to call my abstract method. MyCode : MainActivity.java public class MainActivity extends MyActivity { @Override public void onTest() { Log.d("MyLog", "onTest"); } } MyActivity.java public abstract class MyActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } public abstract void onTest(); } So this is the above code snippet ,

I have read python docs about abstract base classes: From here : abc.abstractmethod(function) A decorator indicating abstract methods. Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it. A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods and properties are overridden. And here You can apply the @abstractmethod decorator to methods such as draw() that must be implemented; Python will then raise an exception for classes that don’t define the method. Note that the exception is only raised when you

I have an abstract class: abstract class Shape { public String color; public Shape() { } public void setColor(String c) { color = c; } public String getColor() { return color; } public double area() { return 0; } } Which provides non abstract methods and then i want to initialize it like: Shape object = new Shape(); so on initialization, it's still giving me an error, but why? If I provide one abstract method in the class, then it could be understandable that the class cannot be initialized. In this situation, why is it still giving an error? Any help would be appreciated initialization its

I have some basic questions about abstract classes/methods.I know basic use of abstract classes is to create templates for future classes. But are there any more uses of them ? When should you prefer them over interfaces and when not ? Also when are abstract methods useful ? I know basic use of abstract classes is to create templates for future classes. But are there any more uses of them? Not only can you define a template for children, but Abstract Classes offer the added benefit of letting you define functionality that your child classes can utilize later. You can't provide an