C++如何访问由Composition创建的矢量数据？

Question

我会直接进入一个例子，我认为它更容易失败。 音乐Cd有曲目。如何访问音乐Cd类中的“TrackInfo”矢量（XTrackInfo）数据？ 我想打印，甚至改变价值观，我不知道如何。 感谢

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

#include <iterator> 
#include <numeric> 



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: 

    std::string m_Author; 
    std::vector<XTrackInfo> m_TrackInfo; 

public: 

    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; } 
    const std::vector<XTrackInfo> GetTracks() const { return m_TrackInfo;} 

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


    void AddTrack(XTrackInfo NewTrack){ 

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

    } 


}; 



void PrintCdContents(const XMusicCd& Cd) 
{ 

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

    //problems here :) 


} 

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); 
} 

Answer 1

使用迭代器：

std::vector<XTrackInfo> tracks = Cd.GetTracks(); 
for (std::vector<XTrackInfo>::const_iterator it = tracks.begin(); it != tracks.end(); ++it) { 
    std::cout << it->GetTrackName() << std::endl; 
} 

或索引：

std::vector<XTrackInfo> tracks = Cd.GetTracks(); 
for (unsigned i = 0; i < tracks.size(); ++i) { 
    std::cout << tracks.at(i).GetTrackName() << std::endl; 
}