How can I edit comment meta value before it is saved?

Question

I have introduced a custom field in comments form using add_comment_meta() function.

I would like to know if there is a way to edit the data of the comment meta just before the post data is saved so that every time the data is replaced with my value before it is saved.

Lets say that the key is brand_id.

I have used the following function to edit the custom_meta Value

function update_comments_meta($post_id) {
    $args = array(
        'post_id' => $post_id,
    );
    $comments = get_comments($args);
    if (!empty($comments)) {
        foreach ($comments as $comment) {
            echo $comment;
            update_comment_meta($comment->comment_ID, 'brand_id', 'hard_coder');
        }
    }
}

add_action('save_post', 'update_comments_meta');

Answer 1

You can use "save_post" action-hook

Add the code below into functions.php and enchance with your comment_meta code.

function update_comments_meta( $post_id ) {
   // Do whatever add/update_comment_meta code you need
}
add_action( 'save_post', 'update_comments_meta' );

---

UPDATE.

As an example i've attach code below. It performs on post save/update action fired. Code gets current post comments (all) then looping through received comment object it launch update_comment_meta with ID extracted from comments object.

function update_comments_meta($post_id) {
    $args = array(
        'post_id' => $post_id,
    );
    $comments = get_comments($args);
    if (!empty($comments))
        foreach ($comments as $comment) {
            update_comment_meta($comment->comment_ID, 'YOUR_META_KEY', 'YOUR_META_VALUE');
        }
}

add_action('save_post', 'update_comments_meta');

Hope this is the case that you where interested in. Code tested on 4.3 twentyfifteen.

Refferences:

1. update_comment_meta()
2. get_comments()