Passing a string vector to a function
You need to move vector<string> from one function to another function and work with it there.
I was able to do this with data like int, but it doesn't work with string.
std::string fun(std::string);
int main()
{
std::vector<std::string> arr(3);
fun(arr);
std::cout << "Сумма: " << fun(arr);
system("pause");
}
std::string fun(std::string arr) {
for (int i = 0; i < 3; i++) {
std::cout << "[" << i + 1 << "] ";
std::cin >> arr[i];
}
return arr;
}
P.S. I know that I have an error in my code, I just want to understand the essence of how to pass the contents of a vector to a function.
3 answers
It is best to transmit by reference. Imagine what happens when passing by value - each row is copied, and a heap of memory is allocated (a very slow operation)... And then - whatever you do with this vector of strings in the function-it will not affect the original. Sometimes it's not the right thing to do. So I recommend
std::string fun(std::vector<std::string>& arr)
If you need to somehow change this vector and strings, or
std::string fun(const std::vector<std::string>& arr);
If arr, if you don't need to change it.
In your particular case - the first call in general completely loses everything entered, the second returns the same vector - i.e. the next copy of everything when returning! (I'm not saying yet that std::cout << "Сумма: " << fun(arr); doesn't compile due to the lack of an output operator for the string vector). After that, you have a vector returned by the function fun(arr), and a vector arr that has nothing to do with this returned vector .
In short, in this code of yours, passing the argument only as a non-const reference.
Here is an example with a link transfer. In my opinion, the return of the string for this function is not needed.
#include <iostream>
#include <string>
#include <vector>
using namespace std;
ostream& operator<<(ostream &os, const vector<string> &v)
{
for(auto const& s: v) os << s << " ";
return os;
}
void fun(vector<string>& arr)
{
for (int i = 0; i < 3; i++) {
cout << "[" << i + 1 << "] ";
cin >> arr[i];
}
}
int main()
{
vector<string> arr(3);
fun(arr);
cout << "result=" << arr << endl;
return 0;
}
It will give you:
[1] 123
[2] 456
[3] 789
result=123 456 789
std::string fun(std::string arr) //функция принимает строку
std::string fun(std::vector<std::string> arr) //функция принимает вектор строк