inheritance

问题 I know this question was asked several time, but i don't find how to resolve it. I get this error when i'm trying to build my project: error LNK2019: unresolved external symbol "public: virtual __thiscall IGameState::~IGameState(void)" (??1IGameState@@UAE@XZ) in function "public: virtual __thiscall MenuState::~MenuState(void)" (??1MenuState@@UAE@XZ) Here is my code: IGameState.h class IGameState { public: virtual ~IGameState(); virtual void update() = 0; virtual void render() = 0; };

问题 I've spent quite a few hours researching and trying to figure out why I'm getting this error. Basically the three files that have to do with the inheriting are CollegeMember.h, Employee.h, and EmpAcademicRecord.h. Employee. is inheriting from CollegeMember.h and EmpAcademicRecord.h is inheriting from Employee.h. Like this CollegeMember <- Employee <- EmpAcademicRecord. The error occurs in EmpAcademicRecord.h. Heres the three files. CollegeMember.h #include <cstdlib> #include <iostream>

问题 Consider the following code snippets: package vehicle; public abstract class AbstractVehicle { protected int speedFactor() { return 5; } } package car; import vehicle.AbstractVehicle; public class SedanCar extends AbstractVehicle { public static void main(String[] args) { SedanCar sedan = new SedanCar(); sedan .speedFactor(); AbstractVehicle vehicle = new SedanCar(); // vehicle //WON'T compile // .speedFactor(); } } SedanCar is a subclass of AbstractVehicle which contains a protected method

问题 Consider the following code snippets: package vehicle; public abstract class AbstractVehicle { protected int speedFactor() { return 5; } } package car; import vehicle.AbstractVehicle; public class SedanCar extends AbstractVehicle { public static void main(String[] args) { SedanCar sedan = new SedanCar(); sedan .speedFactor(); AbstractVehicle vehicle = new SedanCar(); // vehicle //WON'T compile // .speedFactor(); } } SedanCar is a subclass of AbstractVehicle which contains a protected method

问题 The initialization process of a group of classes that share a common parent can be divided into three parts: Common initialization Subclass-specific initialization Common post-initialization Currently the first two parts are called from the __init__ method of each child class, but the final post-initialization part has to be called separately, for example class BaseClass: def __init__(self): print 'base __init__' self.common1() def common1(self): print 'common 1' def finalizeInitialization

问题 The initialization process of a group of classes that share a common parent can be divided into three parts: Common initialization Subclass-specific initialization Common post-initialization Currently the first two parts are called from the __init__ method of each child class, but the final post-initialization part has to be called separately, for example class BaseClass: def __init__(self): print 'base __init__' self.common1() def common1(self): print 'common 1' def finalizeInitialization

问题 The initialization process of a group of classes that share a common parent can be divided into three parts: Common initialization Subclass-specific initialization Common post-initialization Currently the first two parts are called from the __init__ method of each child class, but the final post-initialization part has to be called separately, for example class BaseClass: def __init__(self): print 'base __init__' self.common1() def common1(self): print 'common 1' def finalizeInitialization

问题 The initialization process of a group of classes that share a common parent can be divided into three parts: Common initialization Subclass-specific initialization Common post-initialization Currently the first two parts are called from the __init__ method of each child class, but the final post-initialization part has to be called separately, for example class BaseClass: def __init__(self): print 'base __init__' self.common1() def common1(self): print 'common 1' def finalizeInitialization

问题 The initialization process of a group of classes that share a common parent can be divided into three parts: Common initialization Subclass-specific initialization Common post-initialization Currently the first two parts are called from the __init__ method of each child class, but the final post-initialization part has to be called separately, for example class BaseClass: def __init__(self): print 'base __init__' self.common1() def common1(self): print 'common 1' def finalizeInitialization

来源： https://stackoverflow.com/questions/64358862/need-help-writing-a-method-that-returns-the-first-and-last-day-of-a-passed-month