use push_back demonstrates

cpp_move_copy.cc

#include <iostream>
#include <ostream>
#include <string>
#include <vector>
//comment this define to see reallocate
#define F4
class Test {
    public:
        std::string tag;
        Test(std::string &t) : tag(t) {
            std::cout << "Constructed" << '\n';
        };
        Test(std::string &&t) : tag(t) {
            std::cout << "Move Constructed" << '\n';
        };
        Test(const Test &other) : tag(other.tag) {
            std::cout << "Copyed" << '\n';
        };
        Test(Test &&rr) : tag(std::move(rr.tag)) {
            std::cout << "Moved" << '\n';
        };
        Test& operator=(const Test& other){
            tag = other.tag;
            std::cout << "assigned" << '\n';
            return *this;
        };
};
std::ostream& operator<<(std::ostream& out, const Test& t) {
    out << t.tag;
    return out;
}
int main() {
    std::vector<Test> v;
    std::cout << "capacity: " << v.capacity() << '\n';
#ifdef F4
    v.reserve(4);
#endif
    std::string s("test1");
    Test t(s);
    v.push_back(t);
    std::cout << "capacity: " << v.capacity() << '\n';

    std::string s2("test2");
    Test t2(s2);
    v.push_back(std::move(t2));
    std::cout << "capacity: " << v.capacity() << '\n';

    v.push_back(Test(std::string("test3")));
    std::cout << "capacity: " << v.capacity() << '\n';

    std::cout << "List:\n";
    for(auto &a:v)
        std::cout << a << '\n';
    return 0;
}

Output:

capacity: 0
Constructed
Copyed
capacity: 4
Constructed
Moved
capacity: 4
Move Constructed
Moved
capacity: 4
List:
test1
test2
test3