Thread: Learning C++ by Example

I have some dificulties.

I want Xbook inherite from XProduct all the useful attributes.
However, I think that I don't need to create a overload constructor to Xbook with Price, because Price in Xbook class is a function of the label. But, this don't work.

I think that I'm missing some concept, or implementation.

I've updated my git,
https://github.com/CreativeSoftware/LearnCppByExample/

Originally Posted by Elysia

I don't get what you mean. If you have problems, post your code.

Niether I.

I'm trying to understand how can I use this information. I've search in books and I didn't find how can I use at my example.

I have this Xbook class:

Code:

class XBook : public XProduct
{

protected:
    int m_noPages;
    std::string m_label;

public:
    XBook();
    XBook(int BarCode, std::string const Title, std::string const Author,
          std::string const Publisher, int Year,float Price, int NoPages, std::string Label);

    const std::string & GetLabel() const;
    int GetNoPages() const;

    void SetLabel(std::string Label); //only to program
    void SetNoPages(int NoPages);

};class XBook : public XProduct
{

protected:
    int m_noPages;
    std::string m_label;

public:
    XBook();
    XBook(int BarCode, std::string const Title, std::string const Author,
          std::string const Publisher, int Year,float Price, int NoPages, std::string Label);

    const std::string & GetLabel() const;
    int GetNoPages() const;

    void SetLabel(std::string Label); //only to program
    void SetNoPages(int NoPages);

};

With this implementation:

Code:

#include "xbook.h"

XBook::XBook()
{
}

XBook::XBook(int BarCode, const std::string Title, const std::string Author,
             const std::string Publisher, int Year, float Price, int NoPages,
             std::string Label)
    :XProduct(BarCode, Title, Author, Publisher, Year, Price),
      m_noPages(std::move(NoPages)),
      m_label(std::move(Label))
{}

const std::string & XBook::GetLabel()const{
    return m_label;
}

int XBook::GetNoPages() const {
    return m_noPages;
}

void XBook::SetLabel(std::string Label){
    m_label = std::move(Label);
}

void XBook::SetNoPages(int NoPages){
    m_noPages = std::move(NoPages);
}

I have some doubts. Do I need to inherit price from XProduct class? Since I don't wanna let user set the price, instead I want Price be a function of the Label color.

XBook is a XProduct. Can I use directly the Set function from XProduct at XBook?

I think this is basic, However I dind't find any documention about use acessor and mutators with inheritance.
It is basic, but I don't know.

Can I do Something like this?

Code:

#ifndef XBOOK_H
#define XBOOK_H

#include "xproduct.h"


class XBook : public XProduct
{

void setPrice(float Price, std::string Label);

protected:
    int m_noPages;
    std::string m_label;

public:
    XBook();
    XBook(int BarCode, std::string const Title, std::string const Author,
          std::string const Publisher, int Year,float Price, int NoPages, std::string Label);

    const std::string & GetLabel() const;
    int GetNoPages() const;

    void SetLabel(std::string Label);
    void SetNoPages(int NoPages);

};
#endif // XBOOK_H

Code:

#include "xbook.h"

XBook::XBook()
{
}

XBook::XBook(int BarCode, const std::string Title, const std::string Author,
             const std::string Publisher, int Year, float Price, int NoPages,
             std::string Label)
    :XProduct(BarCode, Title, Author, Publisher, Year, Price),
      m_noPages(std::move(NoPages)),
      m_label(std::move(Label))
{}

void XBook::setPrice(float Price, std::string Label){
    if (Label == "Blue"){
        Price = 50;
    }
}
const std::string & XBook::GetLabel()const{
    return m_label;
}

int XBook::GetNoPages() const {
    return m_noPages;
}

void XBook::SetLabel(std::string Label){
    m_label = std::move(Label);
}

void XBook::SetNoPages(int NoPages){
    m_noPages = std::move(NoPages);
}

I've changed my function to:

Code:

void XBook::setPrice(std::string Label){
    if (Label == "Blue"){
        m_price = 50.0;
    }
}

In main:

Code:

      XBook book(1002,"title", "great author", "awesome pub", 2004, 40, 300, "Blue" );
      book.printProductData();

The output price remains 40 .

Originally Posted by Elysia

Come on! You didn't even call SetPrice! Follow the flow of the code!

You suggest setprice at book be private. I cannot call at main. SHould I call it at cpp ?

Thank you for your time.
I've started digging into example, however I've figured it out that it didn't compile.

Code:

../derivedClasses/main.cpp:10:21: error: pure-specifier on function-definition
     virtual ~Base() = 0 {} // Make Base an abstract class -
                     ^
make: *** [main.o] Error 1 "