c++ - 如何在其他变量中加入2个变量

Question

看例子理解

int rnd = rand() %10;
string Folder = "c://foldername";
string final_name = Folder + rnd; // here the target

/* I want the result like that (random folder name)
foldername5
foldername10
foldername3
foldername20
foldername17
*/

Answer 1

将 std::stringstream 用作:

#include <sstream> //include this

std::stringstream ss;
ss << Folder  << rnd;
string final_name = ss.str();

或者你可以只写一行:

string final_name = stringbuilder() << Folder  << rnd;

它需要一个小的实用类:

struct stringbuilder
{
   std::stringstream ss;
   template<typename T>
   stringbuilder & operator << (const T &data)
   {
        ss << data;
        return *this;
   }
   operator std::string() { return ss.str(); }
};

使用这个类，你可以创建 std::string 作为:

void f(const std::string & file ) {}

f(stringbuilder() << Folder  << rnd);

std::string s = stringbuilder() << 25  << " is greater than " << 5 ;