abstract-class

问题 I have the following classes, Base and Derived and when I compile the compiler complains that it cannot create an instance of DLog because it is abstract. Can someone tell me how I can fix this error? I'm guessing it's because not both pure virtual functions are not implemented in the Derived. class Logger { public: virtual void log(int debugLevel, char* fmt, ...) = 0; virtual void log(string logText, int debugLevel, string threadName = "") = 0; static Logger* defaultLogger() {return m

问题 The following test code seems to indicate that if a class has two abstract base classes with common pure virtual methods, then these methods are "shared" in the derived class. #include <iostream> #include <string> using namespace std; struct A { virtual string do_a() const = 0; virtual void set_foo(int x) = 0; virtual int get_foo() const = 0; virtual ~A() {} }; struct B { virtual string do_b() const = 0; virtual void set_foo(int x) = 0; virtual int get_foo() const = 0; virtual ~B() {} };

问题 I'm learning OOAD and trying to implement class relationship with inheritance but there is an issue here is the code Parent Class namespace ConsoleApplication1 { abstract class Classification { public abstract string type(); } } 1st Child Class namespace ConsoleApplication1 { class FullTime : Classification { bool inCampus; string roomDetail; float rent; public FullTime(string studentRoomDetail, float studentRent) { this.inCampus = true; this.roomDetail = studentRoomDetail; this.rent =

问题 Say I'm trying to translate the below Java classes to GNU Smalltalk: public abstract class Account { protected String number; protected Customer customer; protected double balance; public abstract void accrue(double rate); public double balance() { return balance; } public void deposit(double amount) { balance += amount; } public void withdraw(double amount) { balance -= amount; } public String toString() { return number + ":" + customer + ":" + balance; } } public class SavingsAccount

问题 I am trying to create a program that takes food order and prints it out. I have my base class Food which has a pure virtual function in it. Class Food has 2 subclass Pizza and Dessert . I am trying to make an array of Food in my main so when a customer orders Pizza or Dessert , it will be stored in the array of Food . But every time I try, I get an error. How should I put the two items together then if I want to use a loop to go over each item the customer ordered? This is my code: int main()

问题 I'm trying to create an abstract class with generic parameter which will have subclasses which should call methods without having to specify type parameters . I have this so far: abstract class AbstractClass<T : Any> @Autowired constructor(protected val delegate: MyService) { inline fun <T: Any> myMethod(param: Any): T? { return delegate.myMethod(param).`as`(T::class.java) } } And implementation: class TesterWork @Autowired constructor(delegate: MyService) : AbstractClass<Tester>(delegate) {

问题 I am little confused about abstraction in java. I have checked many pages stating that abstraction is data hiding(Hiding the implementation). What I understand about abstraction is it is 'partial implementation'. Just define what you are going to need in an abstract class/interface and afterwards extend/implement them and add your own functionality. What I don't understand is how this is a data hiding? You are going to get access to the code once you implement the class/interface and you will

问题 I am little confused about abstraction in java. I have checked many pages stating that abstraction is data hiding(Hiding the implementation). What I understand about abstraction is it is 'partial implementation'. Just define what you are going to need in an abstract class/interface and afterwards extend/implement them and add your own functionality. What I don't understand is how this is a data hiding? You are going to get access to the code once you implement the class/interface and you will

问题 I have a simple Email() class. It's used to send out emails from my website. <? Email::send($to, $subj, $msg, $options); ?> I also have a bunch of email templates written in plain HTML pierced with a few PHP variables. E.g. /inc/email/templates/account_created.php : <p>Dear <?=$name?>,</p> <p>Thank you for creating an account at <?=$SITE_NAME?>. To login use the link below:</p> <p><a href="https://<?=$SITE_URL?>/account" target="_blank"><?=$SITE_NAME?>/account</a></p> In order to have the PHP

问题 I am a little bit familiar with the difference between Abstract and Interface classes but What do you think is the meaning of the sentence below? An interface can only define constants while abstract class can have fields. 回答1: An interface can only define constants while abstract class can have fields. your field from interface is by implicitly public , static , final which isn't case with abstract class 回答2: constants - static, not changing ( static final ) fields - instance-specific,