C++ :: Inheritance - Using Base Class Constructor (LNK2019 Error)
Sep 16, 2014
I am trying to create a few subclasses which all use the base class constructor, according to my book this is all fine and dandy by using the "using Baseclass::Baseclass", this doesnt work for me.
class Monster {
public:
Monster(char[], char[], char[], int); //The constructor, and its implemented.
etc..
};
[Code] ....
Yet, i recieve this error:
error LNK2019: unresolved external symbol "public: __thiscall Human::Human(char * const,char * const,char * const,int)"
Why is this? Does doing it this way create const pointers somehow? The constructor works fine with Monster, i am using the same calls, just changed to create Human instead of Monster. All files are included where they should, monster and human are declared in the same header.
I have couple of objects which are using some amount of methods. Right now my application is not OOP and i am going to transfer it to OOP. So i would create each class for my each object. Almost all methods are in use for each object, the only one thing which is changing some of those objects passing not all parameters inside specific method. I can go two ways one is prepare interface for all methods i got and each of my classes could implement its own definition for it but other way almost all would implement exactly the same methods but with different parameters so maybe its better to create base class then for each object do inheritance from base class (polymorphism). inside base class i can prepare base methods and classes which will inherit from that class would override those methods for requirements they want.
So imagine: You got:
Memory CPU Latency
and all of them using mostly all of those same methods (only arguments for one of them could be use different way):
Base class: Stuff prop: name, id, date ... methods to ovveride: ExecuteQuery(), ExportToExcel() ...
classes: CPU, Memory, Latency (inheriting from Stuff) ovveride methods and align its definition for specific class use (remember mostly only passing args are used or not by specific class)
The most important thing is that those every objects mostly using all of those methods and what is diffrence that one object can use all of available parameters inside this method and other one no. What i should do? Go with interface or inheritance and polymporfizm inside base class?
I have a simple question about inheritance. Consider the following code:
Code: Class Base { int type; Base(){}; }; Class Derived1 : public Base
[Code] ....
I get the following error: Class "Base" has no member "Function1";
That makes sense - as Base has not declared Function1. But how can I loop through a vector of Bases, and then if the object is of type Derived1, call the function Function1?
I'm trying to implement a decision tree that gets doubles as input (in this sample code just random numbers) and returns a boolean value. At the nodes, I'd like to use various operators that can have different input and return types. I've implemented an abstract base class for the nodes and I'm deriving the specific nodes from it. In the code below, I've included only a few derived classes. Building the tree (randomly) is no problem. However, I'm looking for a clever way to evaluate the tree. I think that uncommenting the lines in bold print would in principle do it. However, this is not possible because "value" is not a member of the base class. The type of "value" is different in the derived classes, so I cannot simply declare it in the base class.
"Node.h" #pragma once class NodeBase{ public: NodeBase* Child_1; NodeBase* Child_2; virtual void evaluate() = 0;
Constructor of the Base Class Person::Person(char* n="", char* nat="U.S.A", int s=1) { name = n; nationality = nat; sex = s; }
Constructor of the Derived Class (inherited from the base class)
Student(char* n, int s=0, char* i=""): Person(n, s)
Why the initialized list of the base class constructor doesn't match the initialized list of the derived class constructor? I know this book is a little bit old, I'm not sure if this wrong in VC++ 2010?
Let's say I have a Car object , and it contains inner Engine object.
Code: struct Car{ Engine mEngine; };
In order to initialize the engine object NOT by the default constructor (if it has any) , we use initialization semantics:
Code: Car::Car: mEngin(arg1,arg2,...) { other stuff here }
Now it gets tricky: Let's say a Car objects has 10 inner objects, each object has about 5 variables in it . Car is a base class for , e.g. , Toyota class. you don't want the Car class to have a constructor with 50 arguments. Can the inner objects of Car be initialized from the base class , e.g. Toyota?
Code: class Toyota: Car(...), mEngine(...), mGear(..) { ... };
The other options are: 1) like said , create a Car constructor which gets 50 arguments, then initialize Car as whole from Toyota - the code becomes less readable and less intuitive 2) Car constructor which get built-objects as arguments and initialize the inner objects with copy constructor . the code gets more readable but then you create many excess objects .
class Base { char * ptr; public: Base(){} Base(char * str)
[code].....
Obj1 is a derived class object where base class char pointer is initialized with "singh" and derived class char pointer is initilized with "sunil". I want to create Obj2 out of Obj1. Separate memory should be created for Obj2 char pointer (base part and derived part as well) and that should be initialized with the strings contained in Obj1.
Here the problem is: Derived class part can be initialized with copy constructor. How to initialize the base class char poniter of Obj2 with the base class part of Obj1. char pointers in both the classes are private.
I tried using initializer list but could not succeed.
I have 2 classes with a Function with the same definition (both inherited from the same base class) and in my derived class I derive from both of those 2. Is it possible to use the Methods of both classes? for example with an other name?
class A { protected: int print(int a) { std::cout << "int A: " << a << std::endl; } }; class B : A
[Code] ....
is there something like using C::print as printc;?
The Problem, I have a Sprite class that derives from a Rectangle with properties Position, Size, Origin and Angle and a Text class that derives from Rectangle. Now i have a Button class deriving from both Sprite and Text.
- The Position, when moving the Button i have to change the position of both so i Implemented a new Method which calls SetPosition from the Sprite and the Text. - The SetSize just affects the Button so i just did using Sprite::SetSize; - The angle affects both so i just implemented a new Method and hide the other two
The problem is here: - The Origin: writing button.SetOrigin(-1,0) should set the Origin of the Button and writing button.SetTextOrigin should set the Origin of the text.
Should i just reimplement a Mehtod named SetTextOrigin and call Text::SetOrigin from there and hide the button.Text::SetOrigin or is there something like using Text::SetOrigin as SetTextOrigin?
I am currently working on an Account login system and when I run the program I receive this error message:
error LNK2019: unresolved external symbol
If you want to see the full code of the source file just ask
const int NUM_OF_ACCOUNTS = 1; Account *account = new Account[NUM_OF_ACCOUNTS]; int AccountSearch(int number, string password); foundAccount = AccountSearch(aNumSearch, passSearch); int AccountSearch(int n, string p); { int x = 0;
I have an odd compiling error. My base class is all delcared and read to go. But I could not figure out how to get my sub classes inherit from it. So I had to make everything public. Even inheriting using the protected inheritance thingy, still could not get them to inherit from that base class.
So I compiled the program, and no other class came back with an error. only my base class. Here is the base class:
#include <iostream> #include <string> using namespace std; class Bankaccount {
[Code] .....
The error I'm getting is saying:
error C2143: syntax error : missing ';' before 'using' Where is there anything needing a semicolon before using?
'Bankaccount' : 'class' type redefinition see declaration of 'Bankaccount'
Is it saying this because I don't have any private class members?
'Bankaccount' : base class undefined
But it is defined.
What is the issue with this class? And how can I get it to compile and run?
I have the following classes and 'dreaded diamond':
A / / B C / / D | | E
Classes B & C both inherit from A using public virtual A.
E is the only concrete class. None of the classes are totally abstract.
Every class has a copy constructor.
All of the copy constructors are chained together through the initialization lists.
E correctly calls D's copy constructor.
D correctly calls B and C's copy constructors.
But neither B nor C call A's copy constructor, although A's default constructor is called. To reiterate B and C have a call to A's copy constructor in their initialization lists.
I guess A's default constructor is being called is because of virtual inheritence, but why isn't its copy constructor called (too)?
A's copy constructor includes some very important code and I could do with calling it. Should I call it from the concrete class' initialization list or is that considered bad form?
I am working on building a set of templated data structures for my own learning and have run in to an error when instantiating my templated linked list. I receive the following error:
error LNK2019: unresolved external symbol "public: __thiscall LinkedList<int>::~LinkedList<int>(void)" (??1?$LinkedList@H@@QAE@XZ) referenced in function _main
--LinkedList.h-- #ifndef LINKEDLIST_H #define LINKEDLIST_H template<class T> class LinkedList {
Code: #ifndef DUCK_H_ #define DUCK_H_ #include<iostream> using namespace std; class Duck
[Code].....
When I compile, it says: "error: 'virtual void Duck::display()' is protected" how come I can't gain access to MallardDuck's display(), which is public?
Shape base class, line and Point derived classes. What should I declare in .h files and implement in .cpp files that this is array will be work.
My major concern refer to operator [] and assign (=) operator. As far as I understand I should overload ([]) and (=) three times for classes shape , line and point or not... or is it possible made through virtual function? How will be code looks like ?
Code: // part of main.cpp Shape* shapes[3]; // Array of pointers to Shape shapes[0] = new Shape(); shapes[1] = new Line ("line from array ", Point(1,22),Point(33,22)); shapes[2] = new Point(11,44); cout << "using ToString function" << endl; for(int i=0; i < 3; i++) cout << s[i]->ToString(); for(i=0; i < 3; i++) delete s[i];
I am having some serious issues with class inheritance. I am trying to make a MoneyBag class inherit from a class called bag. This will not work. I get an error complaining: error: expected class-name before '{' token. And yes I have googleing it and tried several of the various solutions offered with no avail.
The MoneyBag is pretty simple right now as I wanted to get it connected to bag before I tried to do anything with it.
//MoneyBag.h//
#ifndef MONEYBAG_H #define MONEYBAG_H #include <bag.h> class MoneyBag : public bag{ ////<<------ Error appears on this line.
[Code] ....
So based on everything I have seen on line the statement: class MoneyBag : public bag{ is legal. As it is done this way on this very site's tutorial: class Rectangle: public Shape, public PaintCost{
I've been working on a program that uses a reference counting class that I've written which works fine for objects that inherit from it however I now need to have the following setup:
class SBComponent : private Refcounted { /*stuff*/} class ProxiedComponent : public SBComponent, private Refcounted {/*stuff*/}
The compiler gives the following warnings
warning: direct base ‘Refcounted’ inaccessible in ‘ProxiedComponent’ due to ambiguity
And then several repeats of the error:
error: request for member ‘bk’ is ambiguous Back *b = bk<ProxiedComponent>();
bk is a templated function that's defined in Refcounted and returns a pointer of type <template arg>::Back (ProxiedComponent::Back in this case).
I don't understand why the call to bk is ambiguous as although there's two instances of Refcounted (there needs to be with the way I've designed it so I can't make it virtual) it's inheritance is private in both cases so there should only be one instance of it visible in ProxiedComponent.
In this assignment the student should develop a month calendar by designing a class called calendarType . This class uses two other classes (dateType and dayType) as described below:
1. dayType Class: This class has been designed by students in Lab1 exercises. Referee to it. 2. dateType Class: This class is designed and implemented to keep track of data. This class has been provided it to you. Study it first then add definitions and implementations of the following operations to this class:
- Test whether the year is a leap year. Leap year is identified by 3 criteria : - The year is evenly divisible by 4; - If the year can be evenly divided by 100, it is NOT a leap year, unless; - The year is also evenly divisible by 400. Then it is a leap year. - Return the number of days in the month. For example, if the date is 12/3/2014, the number of days to be returned is 31 because there are 31 days in March. - Return the number of days passed in the year. For example, if the date is 18/3/2014 the number of days passed is 77. Note that the number of days returned also includes the current day. - Return the number of days remaining in the year. For example, if the date is 18/3/2014 , the number of days remaining in the year is 288. - Calculate the new date by adding a fixed number of days to the date. For example, if the date is 18/3/2014 and the days to be added are 25, the new date is 12/4/2014.
To print monthly calendar using calendarType class, you must know the first day of the month and the number of the days in that month. Thus, you must store the first day of the month, which is in the form of dayType and the month and the year of the calendar. Clearly, the month and the year can be stored as an object of the form dateType by setting the day component of the date to 1, and the month and year as specified by user.
Design the class calendarType so that the program print a calendar for any month starting 1/1/ 1500 which is Monday. To calculate the first day of a month, you can add the 2 appropriate days to Monday of January 1, 1500. For this class identify and implement the following operations:
- Determine the first day of the month for which the calendar will be printed. Call this operation firstDayOfMonth. - set/get month. - set/get year. - Print calendar for particular month. - Add the appropriate constructors to initialize the member variables. - Write a test program to print the calendar for either a particular year or a particular month.
Say in my main class, I have a function fight(Player p1, Player p2) and I would like to do something like this in the fight function, given that p1 is the human and p2 is the computer:
//function fight() fight(Player p1, Player p2) { p1.func2(); } //using function fight() fight(human, computer);
When I compile the program, I got this: error: ‘class Player’ has no member named 'func2()' What can I do to allow p1 to call func2 inside fight()? I'm not allowed to use pointers as the parameter for fight() and have to use the signature fight(Player p1, Player p2).
The compiler creates virtual table for the base class and also for the derived class whether we override it or not.
That means each class has separate virtual table. when we get the size of the each class with out any data members... the size of base is -- 4 bytes(64 bit) and the size of derived is -- 1
The size of base class 4 is correct since it creates the virtual pointer internally and its size is member data + virtual pointer, but it in this case I have included any data members so it has given 4 byts.
But why in case of derived is 1 byte, since it the derived class has overridden the virtual function from base, this will also contains the virtual pointer which will be pointing to derived class Vtable, it the size of the class suppose to be 4 instead of 1 byte.
#include <iostream> #include "curve1.h" #include "curve2.h" using namespace std; int main() { Curve1 curve1Obj; Curve2 curve2Obj;
[Code]...
Base class Score has two derived classes Curve1 and Curve2. There are two curve() functions, one is in Curve1 and other in Curve2 classes. getSize() returns the value of iSize.
My base class header score.h looks like this:
#ifndef SCORE_H #define SCORE_H class Score { private: int *ipScore; float fAverage; int iSize;
[Code]...
You can see that I have used curve1Obj to enter scores, calculate average and output. So if I call getSize() function with cuve1Obj, it gives the right size that I took from user in enterScores() function. Also the result is same if I call getSize() in score.cpp definition file in any of the functions (obviously). .....
The problem is when I call curve() function of Curve2 class in main (line 23) with the object curve2Obj, it creates a new set of ipScore, fAverage and iSize (i think?) with garbage values. So when I call getSize() in curve() definition in curve2.cpp, it outputs the garbage. .....
How can I cause it to return the old values that are set in curve1.cpp?
Here is my curve2.cpp
#include <iostream> #include "curve2.h" using namespace std; void Curve2::curve() { cout << "getSize() returns: " << getSize() << endl; // out comes the garbage }
Can I use a function to simply put values from old to new variables? If yes then how?
In this book, item 3 is about never treat arrays polymorphically. In the latter part of this item, the author talks about the result of deleting an array of derived class objects through a base class pointer is undefined. What does it mean? I have an example here,
Code: class B { public: B():_y(1){} virtual ~B() { cout<<"~B()"<<endl;
[Code] ....
This sample code does exactly what I want. So does the author mean the way I did is undefined?
#include <iostream> using namespace std; class superclass; class subclass1; class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
