如何打印出對象的矢量元素？

Question

我想創建一個測驗銀行遊戲....我有一個txt文件，存儲信息並將其推回到矢量，但我的主要問題是如何打印出我的get方法與這個指向矢量對象的指針？ 這是我整個代碼

#include <iostream> 
#include <string> 
#include <fstream> 
#include <iostream> 
#include <string> 
#include <vector> 
#include <cstdlib> 
using namespace std; 
class question 
{ 
private : 
    string ques ; 
    string answer; 
    int point ; 
public : 
    question(string ques = "",string answer = "",int point = 0):ques(ques),answer(answer),point(point){} 

    virtual string getAnswer() = 0; 
    virtual string getQuestion() = 0; 
    virtual int getPoint() = 0; 



}; 

class SAquestion : public question 
{ 
private : 
    string ques ; 
    string answer; 
    int point ; 
public : 
SAquestion(string ques = "",string answer = "",int point = 0):ques(ques),answer(answer),point(point){} 
    string getAnswer() {return answer;} 
    string getQuestion(){return ques ;} 
    int getPoint() {return point ;} 



}; 
class MCquestion : public question 
{ 
private : 
    string ques ; 
    string answer; 
    int point ; 
public : 
MCquestion(string ques = "",string answer = "",int point = 0):ques(ques),answer(answer),point(point){} 
    string getAnswer() {return answer;} 
    string getQuestion(){return ques ;} 
    int getPoint() {return point ;} 



}; 

class TFquestion : public question 
{ 
private : 
    string ques ; 
    string answer; 
    int point ; 
public : 
TFquestion(string ques = "",string answer = "",int point = 0):ques(ques),answer(answer),point(point){} 
    string getAnswer() {return answer;} 
    string getQuestion(){return ques ;} 
    int getPoint() {return point ;} 



}; 


void readDataByDelimiter(const char* filename, vector< SAquestion>*SHORTQ) { 
    string line; 
    ifstream ifs(filename); 
    if (ifs.is_open()) { 
     cout << "Reading data...\n"; 
     int c = 0; 
     while (getline (ifs,line) && (*line.c_str() != '\0')) { 
      string delimiter = ","; 
      size_t pos = 0; 
      string* token = new string[5]; 
      int f = -1; 
      while ((pos = line.find(delimiter)) != string::npos) { 
       token[++f] = line.substr(0, pos); 
       cout << " " << token[f] << " | " ; 
       line.erase(0, pos + delimiter.length()); 
      } 
      token[++f] = line; 
      cout << token[f] << endl;  // last item in string 
      c++; 

      // push to vector (numerical data converted to int) 
      SAquestion b(token[1], token[2], atoi(token[3].c_str())); 
      SHORTQ->push_back(b); 
     } 
     cout << c << " row(s) read." << endl << endl; 
     ifs.close(); 
    } 
    else 
     cout << "Unable to open file"; 
} 

    enter code here 


int main() 
{ 
    vector<SAquestion> *s = new vector<SAquestion>(); 
    readDataByDelimiter("SHORQ.txt", s); 
cout <<s[0]->getAnswer(); 


} 

- List item 

Answer 1

這裏是代碼打印vector：

void Print_Vector(const std::vector<SAquestion>& v) 
{ 
    std::vector<SAquestion>::const_iter iter; 
    const std::vector<SAquestion>::const_iter end_iter = v.end(); 
    for (iter = v.begin(); iter != end_iter; ++iter) 
    { 
    cout << *iter << "\n"; 
    } 
} 

上面的代碼使用了迭代每個元素參觀了vector。由於打印不會改變vector的內容，所以vector通過常數參考和常數使用迭代器。

注意：此功能要求operator <<超載以打印SAquestion項目。

注意：通過使用通過引用，不需要使用指針。

編輯1：重載operator<<
要打印的對象，改變自己的觀點，並有打印對象及其成員。一個方便的方法是重載operator>>：

class SAquestion 
{ 
//... 
    public: 
    friend std::ostream& operator<<(std::ostream& output, const SAquestion& saq); 
}; 
std::ostream& operator<<(std::ostream& output, const SAquestion& saq) 
{ 
    output << "Q: " << saq.ques << "\n"; 
    output << "A: " << saq.answer << "\n"; 
    output << "\n"; 
    return output; 
} 

你並不需要使用getAnswer()方法，因爲friend關鍵字允許operator<<功能直接訪問SAquestion成員。