abstract-class

来源： https://stackoverflow.com/questions/21531860/how-to-bind-a-subclass-of-an-abstract-class-in-a-spring-mvc-method

问题 This question already has answers here : Default Interface Methods. What is deep meaningful difference now, between abstract class and interface? [closed] (6 answers) Closed 10 months ago . C# 8.0 has introduced a new language feature – default implementations of interface members. public interface IRobot { void Talk(string message) { Debug.WriteLine(message); } } The new default interface implementations provides the elements of the traits language. However is is also blurring the line

问题 This question already has answers here : Default Interface Methods. What is deep meaningful difference now, between abstract class and interface? [closed] (6 answers) Closed 10 months ago . C# 8.0 has introduced a new language feature – default implementations of interface members. public interface IRobot { void Talk(string message) { Debug.WriteLine(message); } } The new default interface implementations provides the elements of the traits language. However is is also blurring the line

问题 Say I have classes declared like this: public abstract class IdentifiableEntity { public boolean validate() { return true; } } public class PreferenceCategory extends IdentifiableEntity { public boolean validate() { return true; } } Now, let's say I have PreferenceCategory variable created, and I want to call the IdentifiableEntity.validate() method, not the PreferenceCategory.validate() method. I would have thought I could do this with a cast (see below), but it still calls the overridden

问题 I was reading official python documentation. In the mentioned link, the second line states that: Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it. But, I was successfully able to define the below given class. from abc import abstractmethod class A(object): def __init__(self): self.a = 5 @abstractmethod def f(self): return self.a a = A() a.f() So, the code above worked fine. And also, I was able to create a subclass class B(A): def __init__(self): super

问题 I was reading official python documentation. In the mentioned link, the second line states that: Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it. But, I was successfully able to define the below given class. from abc import abstractmethod class A(object): def __init__(self): self.a = 5 @abstractmethod def f(self): return self.a a = A() a.f() So, the code above worked fine. And also, I was able to create a subclass class B(A): def __init__(self): super

问题 This bounty has ended . Answers to this question are eligible for a +50 reputation bounty. Bounty grace period ends in 17 hours . Antonin GAVREL wants to draw more attention to this question. I am almost done with fill in blanks implementation for my app but unfortunately I keep running into layout issues. However as I keep solving the issues I am almost done with it, this is the code so far: RichText( text: TextSpan( text: "dummy", style: TextStyle( color: Colors.white, fontSize: 20, height:

问题 Here is the problem: I keep getting the unimplemented pure virtual method error when trying to compile. I have implemented all of the pure virtual methods in the abstract base class. Any ideas? here is the abstract base class: class record{ public: virtual int getID()=0; virtual record *clone(); }; and the implementation: class sdata: public record{ public: sdata(std::string s = ""){data=s; ID=atoi(data.substr(0,8).c_str());} virtual int getID(){return ID;} private: std::string data; int ID;

问题 Here is the problem: I keep getting the unimplemented pure virtual method error when trying to compile. I have implemented all of the pure virtual methods in the abstract base class. Any ideas? here is the abstract base class: class record{ public: virtual int getID()=0; virtual record *clone(); }; and the implementation: class sdata: public record{ public: sdata(std::string s = ""){data=s; ID=atoi(data.substr(0,8).c_str());} virtual int getID(){return ID;} private: std::string data; int ID;

问题 The following code is a very simple implementation of a SqlAlchemy ORM with one simple table. The Mytable class tries to inherit from BaseAbstract. The code throws the following exception: Message: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases from abc import ABC from sqlalchemy import Column, Integer, create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker class