Thread: Learning C++ by Example

I'm reading the chapter 3 of C++ primer 5th edition book. I'll doing all exercises.
I think that I know what the addTrack fcn will do. I don't know (yet) how to implement.

AddTrack function should receive(from overloaded constructor) or create(using setters) a track object and append this object to the vector Tracks of xmusicCd.
So, this is clear, but I think that I'm far way .

I think that i need to use emplace.However I don't know how can I access the Tracks vector.

Ok, there is an update.
I don't know how can I access the Trackinfo Vector inside of Cd class, could you help?

I think the AddFunction is working, but I had to find how to to print to be sure.

Code:

#include <iostream>
#include <vector>
#include <string>

// You may not modify XTrackInfo
class XTrackInfo
{
    std::string m_TrackName;
    int m_Length;

public:
    XTrackInfo() {}

    XTrackInfo(std::string TrackName, int Length):
        m_TrackName(std::move(TrackName)),
        m_Length(Length)
    {}

    void SetTrackName(std::string TrackName) { m_TrackName = std::move(TrackName); }
    void SetTrackLength(int Length) { m_Length = Length; }
    const std::string& GetTrackName() const { return m_TrackName; }
    int GetTrackLength() const { return m_Length; }
};

class XMusicCd
{
private:
    // You may not modify these member variables
    std::string m_Author;
    std::vector<XTrackInfo> m_TrackInfo;

public:
    // You may not modify these member functions
    XMusicCd() {}
    XMusicCd(std::string Author, std::vector<XTrackInfo> Tracks):
        m_Author(std::move(Author)),
        m_TrackInfo(std::move(Tracks))
    {}

    void SetAuthor(std::string Author) { m_Author = std::move(Author); }
    const std::string& GetAuthor() const { return m_Author; }

    int GetLength() const; // Left incomplete on purpose; you will implement it later


    void AddTrack(XTrackInfo NewTrack){
        m_TrackInfo.emplace_back(NewTrack.GetTrackName(),NewTrack.GetTrackLength());

    }


    // Add additional functions to this class as necessary to make it compile.
};



void PrintCdContents(const XMusicCd& Cd)
{
    // Implement this function such that it compiles
    // Also, to be explicit, you may not add any tracks to the CD in here. That is not the purpose of this function. You may also not change the signature of the function.
    // You shall specifically not modify the CD object by calling any setters.
   //Cd.

    std::cout << "Author : " << Cd.GetAuthor() << "\n";
    std::cout << "\n" << std::endl;
    std::cout << "Track Info" << std::endl;
//    for(auto && e: Cd.Tracks){
//        std::cout << e << "\n";}

    // How can I acess the trackinfo vector inside of Cd class?
    //


}

int main()
{
    // You may not change this function
    XMusicCd MyCd;
    MyCd.SetAuthor("Hello World");
    MyCd.AddTrack(XTrackInfo("This is a test", 100));
    MyCd.AddTrack(XTrackInfo("This is a test 2", 200));
    PrintCdContents(MyCd);
}

I don't know how can I access the Trackinfo Vector inside of Cd class, could you help?

You'll need to create a XMusicCd member function to provide access to that vector.



Jim

Originally Posted by Elysia

Consider the operations: "return a list of all tracks" and "print information of all tracks (for debugging purposes)". Both should suit what you need and it's up to you to implement one such function.

I'll try to figure out how can I create an acessor function to the track collection.
I'm not sure. But since the size of TrackInfo vector is unknown, I think that I'll need to use iterators.
Learning OOP is tricky.

Originally Posted by Elysia

>>void AddTrack(XTrackInfo NewTrack)
>>m_TrackInfo.emplace_back(NewTrack.GetTrackName() ,NewTrack.GetTrackLength());
While yes, this looks right, this is slower and more verbose than it needs to be.
This will call the constructor XTrackInfo(std::string TrackName, int Length) in XTrackInfo. But there are other constructors in the class. Which one do we usually call when we want to make a copy of something?

Usually we use the default constructor. Can I do ?:

Code:

m_TrackInfo.emplace_back(NewTrack);

Another thing. Is it correct access directly private variables? For the same reason that you have talked about on the previous post.

Originally Posted by Elysia

Or you can, you know, create a function that prints the debug info you need without having to create an accessor function.
The point is that I want you to ponder about how the interface of such a function--any type of function you would write to do this--would look like.

Since we need print all of info stored at cds I think that is usefull create a function which access inside the vector of trackinfo.
I don't know (yet) how to do it

Originally Posted by Elysia

If you want to user to be able to enumerate the tracks of a CD, you should first familiarize yourself with the iterator pattern.
Then you should create appropriate begin() and end() functions, or at the very least cbegin() and cend().

I was in vacations. I'm lost
But I'll try catch up.
I think that I need more theoretical background and/or doing/seeing more examples.

I think it is time to look into "How to get trackinfo".

I did an update to my code:

Code:

#include <iostream>
#include <vector>
#include <string>

// You may not modify XTrackInfo
class XTrackInfo
{
    std::string m_TrackName;
    int m_Length;

public:
    XTrackInfo() {}

    XTrackInfo(std::string TrackName, int Length):
        m_TrackName(std::move(TrackName)),
        m_Length(Length)
    {}

    void SetTrackName(std::string TrackName) { m_TrackName = std::move(TrackName); }
    void SetTrackLength(int Length) { m_Length = Length; }
    const std::string& GetTrackName() const { return m_TrackName; }
    int GetTrackLength() const { return m_Length; }
};

class XMusicCd
{
private:
    // You may not modify these member variables
    std::string m_Author;
    std::vector<XTrackInfo> m_TrackInfo;

public:
    // You may not modify these member functions
    XMusicCd() {}
    XMusicCd(std::string Author, std::vector<XTrackInfo> Tracks):
        m_Author(std::move(Author)),
        m_TrackInfo(std::move(Tracks))
    {}

    void SetAuthor(std::string Author) { m_Author = std::move(Author); }

    const std::string& GetAuthor() const { return m_Author; }
    XTrackInfo GetTracks(Tracks) const{}

    int GetLength() const; // Left incomplete on purpose; you will implement it later


    void AddTrack(XTrackInfo NewTrack){
        //m_TrackInfo.emplace_back(NewTrack.GetTrackName(),NewTrack.GetTrackLength());

        m_TrackInfo.emplace_back(std::move(NewTrack));

    }


    // Add additional functions to this class as necessary to make it compile.
};



void PrintCdContents(const XMusicCd& Cd)
{
    // Implement this function such that it compiles
    // Also, to be explicit, you may not add any tracks to the CD in here. That is not the purpose of this function. You may also not change the signature of the function.
    // You shall specifically not modify the CD object by calling any setters.
   //Cd.

    std::cout << "Author : " << Cd.GetAuthor() << "\n";
    std::cout << "\n" << std::endl;
    std::cout << "Track Info" << std::endl;

    for (auto it = NewTrack.begin(), end = NewTrack.end(); it != end; ++it)
    {
        std::cout << *it << " ";
    }

    // How can I acess the trackinfo vector inside of Cd class?
    //


}

int main()
{
    // You may not change this function
    XMusicCd MyCd;
    MyCd.SetAuthor("Hello World");
    MyCd.AddTrack(XTrackInfo("This is a test", 100));
    MyCd.AddTrack(XTrackInfo("This is a test 2", 200));
    PrintCdContents(MyCd);
}

It doesn't work, why? I don't figure out how can I create an acessor to the Tracks vector which belongs to cd class.

I think that I need to create a function getTracks which will return the Track contents. Probably the function type will be XTrackInfo type.