assign <char>vector to global std::string

[Ducky]

This is how you can assign <char>vector to std::string when you create the string.

std::vector<char> cVec(length);
. . .
string str(cVec.begin(),cVec.end());

But how do you convert it to a global string? Is it possible or we have to create a second string first?

[Elysia]

What is a "global" string?

[Ducky]

What is a "global" string?

string str; // global variable std::string

int main()
{

...

str <- assign <char> vector;

...


}

[jimblumberg]

Why the global variable?

Do you mean something like:

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

using namespace std;


int main()
{
   // Why a global?
   string str;

   char c = 32;
   std::vector<char> cVect;
   for( int i; i < 5;  ++i)
      cVect.push_back(++c);

   // Print the vector elements.
   for( auto itr : cVect)
      cout << itr << " ";
   std::cout << "\n\n";

   // Copy the vector to the string.
   for(auto itr : cVect)
      str += itr;

   // Print the string.
   cout << str << std::endl;

   return(0);
}

Or you could also use std::copy() if you desired.

Jim

[Ducky]

Yes, or a string declared in main(), doesn't matter.

I tried copy() but it wont copy anything.

str.copy(&cVec[0], cVec.size(), 0);

Should I copy it char by char? Could be time expensive for a large file.

[Codeplug]

>> assign <char>vector to global std::string
Your verb is right on the money: basic_string::assign - C++ Reference

gg

[Ducky]

>> assign <char>vector to global std::string
Your verb is right on the money: basic_string::assign - C++ Reference

gg

Hahaha, yeah, assign() is working! Thanks Codeplug!

And to you to Jim!

[Elysia]

I tried copy() but it wont copy anything.

str.copy(&cVec[0], cVec.size(), 0);

Do you even know how to use std::string::copy? This copies characters FROM string, not TO string.
Regardless, what you can do it either

a) Construct a string with the correct length and read into it directly:
std::string s(my_length, '\0');
// Read into &s[0].

b) If you must assign it to another string that already exists, you can resize it and read directly into it:
my_str.resize(my_length);
// Read into &s[0].

c) With C++11, you can also use a temporary cheaply by moving the result into dest:
std::string s(my_length, '\0');
// Read into &s[0].
dst = std::move(s);

[laserlight]

I note that the first two of Elysia's suggestions in post #8 pertain to doing away with the std::vector<char> and reading into the std::string directly. The third suggestion would be suitable if you really must have a std::vector<char>, but then using the assign member function would be more straightforward.