constructor

问题 So this question adds to my previous question about initializing member vector in an initialization list.. Here are my base & derived class definitions... class Base { public: std::vector<int> m_Vector; } class Derived : public Base { Derived() : m_Vector {1, 2, 3} {} // ERROR when referring to m_Vector } When trying to initialize Derived's m_Vector.. I get an error in Visual Studio saying that "m_Vector" is not a nonstatic data member or base class of class "Derived" Why can't derived class

问题 class A { public A() { System.out.println("Constructor A"); } } class B extends A { public B() { System.out.println("Constructor B"); } } class C extends B { public C() { System.out.println("Constructor C"); } public static void main(String[] args) { C c = new C(); } } When running the code then it calls all constructor but needs to call only child constructor. output like only print Constructor C 回答1: Like the comments and the other answer already said, this is explicitly impossible . If a

问题 I'm learning Java at the moment so I hope this question isn't too obvious. I come from another language which does not have garbage collection. In this other language I sometimes created objects in constructor and then deleted them in the destructor so I could use them for the entire life of the object. As a simplified example, I have a user and a booking class. The booking class references a user but if I create the user in the constructor of the booking class, it dereferences the user once

问题 I'm trying to construct a table with Prototype's New Element function. I was experiencing problems in Firefox when I was updating the thead with the complete content: all th elements plus contents. Firefox was stripping the tags and displays only the contents. Anyways I decided to construct every single th element and then append it to the thead utilizing the Element.update() function. But I haven't found a way to append multiple objects with this function. The th elements look like this: var

问题 I've been banging my head against a wall for sometime on this one. I'm trying to create a class for storing data on People with another class to store their Bank Transactions. Ideally, this all be hidden away and leave only simple statments, declarations and functions available to the programmer. These will include: Dim Clients As New ClientList Clients.Count 'readonly integer Clients.Add("S") Clients.Refresh() Clients(n).Remove() Clients(n).Transaction.Add() Clients(n).Transaction(n).Remove(

问题 public class Ride { public static String name; public static int ticketsRequired; public static float heightRequirement; public Ride(String name, int ticketsRequired, float heightRequirement) { this.name = name; this.ticketsRequired = ticketsRequired; this.heightRequirement = heightRequirement; } public static void main(String args[]) { Ride coaster, tosser; coaster = new Ride("Roller Coaster", 6, 4.25f); tosser = new Ride("Tummy Tosser", 7, 4.9f); } } It only takes the value of the last

问题 I don't get what I'm doing wrong. It's a really simple program I made to practice using headers, classes and constructors. It says that I'm not missing a return type for the function getValue() in Header2.cpp. I have no idea how to fix it. Any ideas? Test.cpp #include <iostream> #include <conio.h> #include "Header2.h" int main() { Thing Implement(1); std::cout << "The truth value is: " << Implement.getValue() << std::flush << "/n"; _getch(); return 0; } Header2.h #ifndef Object_H_ #define

问题 Debug_VLD in VS2010 reveals some memory leaks that come from class member creation / initialization / deletion. my_member is a data member with type double*. In constructor, I have my_member = NULL ; Then in some method, i need to allocate memory for my_member . I cannot do so in constructor, since i dont know size of array yet, and/or size may different for different calls of the method. What i do in this method is checking if member is NULL. if so, i allocate space for it, if not, i can

问题 I usually use isinstance for constructor overloading, but people also suggests @classmethod for the same. But to my knowledge @classmethod shares the variable. Below is a simple class class abc: def __init__(self, a=0): self.a = a @classmethod def from_const(cls, b=30): cls.b = b return cls(10) def printme(self): print(self.a,self.b) Now, lets make three objects a1 = abc(a=100) a2 = abc.from_const(b=31) a3 = abc.from_const(b=41) a4 = abc().from_const(b=51) a5 = abc().from_const(b=61) a1

问题 A while ago, I found in a website some code examples of utility functions that are used when creating , destructing objects, or even when overloading some of their operators . More precisely, the following member functions are mainly used: init, copy, set, and destroy. The init member function is used to initialize all the private members. It's mostly called inside the constructors , e.g. the default or parameter constructor . The copy member function is used to do a deep copy of an object