How can I set class member variable correctly from vector in C++

I'm trying to set a class member variable from STL vector in C++.

But it doesn't work the way I want it to. The variable doesn't change, The variable is the same like before.

Am I programming in the wrong way?

Here's the code.

#include <iostream>
#include <vector>
using namespace std;

class Test {
private:
  std::string name;

public:
  Test();
  Test(std::string p_name);
  std::string getName();
  void setName(std::string p_name);
};

Test::Test() { name = ""; }

Test::Test(std::string p_name) : name(p_name) {}

std::string Test::getName() { return name; }

void Test::setName(std::string p_name) { name = p_name; }

int main() {
  // Initializing vector with values
  vector<Test> tests;

  for (size_t i = 0; i < 10; i++) {
    tests.push_back(Test());
  }

  for (Test test : tests) {
    cout << test.getName() << endl;
    test.setName("a");
  }

  for (Test test : tests) {
    cout << test.getName() << endl;
  }

  return 0;
}

This is the result:

> ./main




















>

Why It doesn't work, and how to fix it?

Solution

You're copying the elements from the vector each time you iterate through it in your loop.

Try changing your code to something like this:

for (auto& test : myTests) {
    test.setName("My new name");
}

In this case, the ampersand (&) marks the variables as a reference, which means you can manipulate it directly.

The way your code is written, you're using the copy-constructor to construce a new object.

You can circumvent this, by adding something like:

public:
    explicit Test(const Test&) = delete;

to your class. This will prevent the copying of the object, which will reduce the likelihood of these types of errors.