解析向量中字符串的數據爲適當的數據類型C++

Question

hello我正在讀取CSV文件中的數據，並已成功解析出數據中的所有字符，現在我需要將每列中的字符串數據轉換爲適當的類型（int，double等）。我有我想要的以下類型聲明，然後從那裏每個變量應該更新爲儘可能多的行，所以我可以採取該變量並將其稱爲程序中的其他地方。請參閱下面

vector<std::vector<std::string> > matrix; 
int a; 
int b; 
int c; 
double c; 
double d; 
double e; 
double f; 
int f; 
double f; 
double f; 
string line; 
ifstream file("mynumbers - Copy.csv"); 

if (!file.is_open()) 
    perror("error while opening file"); 

    getline(file, line, '\n');//get the first line of columns names out 

while (getline(file, line,'\n')) //find the endline charcater 
    { 

     vector<string> vec; 
     string linevec; 
     istringstream ss(line);//allows for parsing each line 

     while (getline(ss, linevec, ',')) 
     { 

      vec.push_back(linevec);//push the parsed data for that line into a vector 
     } 

matrix.emplace_back(vec);//push each parsed line into another vector 
     } 

Answer 1

您可能想檢查您的代碼的常見錯誤。像這樣的東西永遠不會編譯：

int c; 
double c; 

您還沒有main()功能

由於這些錯誤，這可能不適合你的需求完全吻合。假設每行有三個int S，4個double S，一個int，和那麼雙double S，我將宣佈一個「linedata」類像這樣：

#include <iostream> // for std::string 
#include <string> // for std::string 
#include <sstream> // for std::istringstream 
#include <utility> // for std::forward 
#include <fstream> // for std::ifstream 
#include <vector> // for std::vector 
#include <stdexcept> // for std::runtime_error 

class linedata 
{ 
    int a; 
    int b; 
    int c; 
    double d; 
    double e; 
    double f; 
    double g; 
    int h; 
    double i; 
    double j; 

public: 

    // constructs a linedata object 
    linedata(std::string&& line) 
    { 
     std::istringstream ss(std::forward<std::string>(line)); 
     char comma; 
     ss >> a >> std::ws >> comma >> std::ws >> // std::ws discarding extra spaces 
       b >> std::ws >> comma >> std::ws >> 
       c >> std::ws >> comma >> std::ws >> 
       d >> std::ws >> comma >> std::ws >> 
       e >> std::ws >> comma >> std::ws >> 
       f >> std::ws >> comma >> std::ws >> 
       g >> std::ws >> comma >> std::ws >> 
       h >> std::ws >> comma >> std::ws >> 
       i >> std::ws >> comma >> std::ws >> 
       j; 

     // check for errors. throw if it fails to parse 
     if(ss.fail()) throw std::runtime_error("Could not parse line!"); 

     std::cout << a << '\n' << b << '\n' << c << '\n' << d << '\n' << 
        e << '\n' << f << '\n' << g << '\n' << h << '\n' << 
        i << '\n' << j << std::endl; 
    } 
}; 

然後，在main（），您可以嘗試打開文件解析字符串：

int main() 
{ 
    std::vector<linedata> lines; 

    std::ifstream file("mynumbers - Copy.csv"); 
    if(! file.is_open()) 
     // personally I would not use perror because it is part of c and 
     // requires yet another header. I'd use this: 
     std::cerr << "Error occurred: " << std::strerror(errno) << std::endl; 

    std::string myline; 
    std::getline(file,myline); // the '\n' is not necessary. It gets a line. 
           // it already knows to look for '\n'. 

    while(std::getline(file,myline)) 
    { 
     lines.emplace_back(std::move(myline)); 
    } 
}