std::move_iterator in C++ 11

std::move_iterator, introduced in C++11, is an iterator adapter that enables STL algorithms to move elements instead of copying them. It is particularly useful for improving performance when working with movable objects.

• Converts ordinary iterators to support move semantics.
• Helps reduce the overhead of unnecessary copying.

Example: Moving Elements Between Containers

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

int main() {
    vector<string> source = {
        "Hi", "Geeks", "for", "Geeks"
    };

    vector<string> destination;

    cout << "Before move:\n";
    cout << "Source: ";
    for (auto& s : source)
        cout << s << " ";

    cout << "\nDestination: ";
    for (auto& s : destination)
        cout << s << " ";

    copy(make_move_iterator(source.begin()),
         make_move_iterator(source.end()),
         back_inserter(destination));

    cout << "\n\nAfter move:\n";

    cout << "Source: ";
    for (auto& s : source)
        cout << s << " ";

    cout << "\nDestination: ";
    for (auto& s : destination)
        cout << s << " ";

    return 0;
}

Before move:
Source: Hi Geeks for Geeks 
Destination: 

After move:
Source:     
Destination: Hi Geeks for Geeks 

Explanation

• make_move_iterator() converts the normal iterators of source into move iterators.
• std::copy() then moves the elements instead of copying them.
• After the move operation, the elements in the source container remain in a valid but unspecified state.

Syntax

A move iterator can be created using the std::make_move_iterator() helper function:

auto itr = make_move_iterator(container.begin());

It can also be created directly:

std::move_iterator<Container::iterator> itr(container.begin());

Example: Moving a Subrange of Elements

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

int main() {
    vector<int> source = {1, 2, 3, 4, 5};
    vector<int> destination;

    copy(make_move_iterator(source.begin() + 2),
         make_move_iterator(source.end()),
         back_inserter(destination));

    for (int x : destination)
        cout << x << " ";
}

3 4 5 

Explanation: Only the elements from index 2 onward are moved into the destination container.

Advantages of std::move_iterator

std::move_iterator provides several advantages:

• Avoids unnecessary copying of objects.
• Improves performance for large containers.
• Enables STL algorithms to use move semantics.
• Works seamlessly with movable types such as std::string, std::vector, and user-defined classes.

When to Use std::move_iterator

You should use std::move_iterator when:

• Transferring ownership of objects between containers.
• Working with large objects where copying is expensive.
• Optimizing memory usage and performance.
• Using STL algorithms that normally perform copying operations.

Difference Between Normal Iterator and std::move_iterator