How do I avoid iterator invalidation with std::forward_list?

When working with std::forward_list in C++, iterator invalidation can occur when you modify the list. It's important to handle this correctly to avoid runtime errors. The following strategies can help you manage iterator validity:

Use the correct methods: Use methods that do not invalidate iterators, such as std::forward_list::insert_after for insertions and std::forward_list::erase_after for deletions.
Reassign iterators: If you need to erase elements, reassign iterators to ensure they point to valid elements after the operation.
Avoid removing elements while iterating: Instead of removing elements during iteration, consider marking elements for removal and performing clean-up in a separate pass.

Here’s an example demonstrating iterator handling with std::forward_list:


        #include <forward_list>
        #include <iostream>

        int main() {
            std::forward_list my_list = {1, 2, 3, 4, 5};

            // Correct insertion method
            auto it = my_list.insert_after(my_list.before_begin(), 0);

            // Iterate safely
            for (auto iter = my_list.begin(); iter != my_list.end(); ) {
                if (*iter % 2 == 0) {
                    iter = my_list.erase_after(std::prev(iter)); // Erase safely
                } else {
                    ++iter; // Only increment if not erased
                }
            }

            // Print remaining elements
            for (const auto& value : my_list) {
                std::cout << value << " ";
            }

            return 0;
        }

How do I avoid iterator invalidation with std::forward_list?

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How do I avoid iterator invalidation with std::forward_list?

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