How to disallow node authors to change node content if comments were submitted for that node?

Question

On my site we have enquiries (nodes) and price offers (comments). So if there's at least one price offered (a comment submitted) the enquiry details (node) shouldn't be changed. Is there any way to do that?

Answer 1

If coding this is an option, you should look at hook_node_prepare. As mentioned there on the first line:

Act on a node object about to be shown on the add/edit form.

A code snippet idea that could do this for you:

function SOME_MODULE_node_prepare($node) {
  if (isset($node->nid) && $node->type == 'YOUR_CONTENT_TYPE' && $node->comment_count> 0) {
    drupal_set_message('You cannot alter this node anymore', 'warning');
    drupal_goto('node/' . $node->nid);
  }
}

Good luck!

Answer 2

If you don't want to write custom code, you can use the Rules and Flag module for this, as described below.

Step 1: flag nodes with comments

Use the Flag module to create a (global) flag with a label of something like "Has price offers".

Step 2: register comment submission

Use Rules to create a custom rule with Rules Event "After saving a new comment.".

This rule should perform a Rules Action "Flag node" (using the flag created in step 1).

Step 3: disallow edits for nodes that have price offers

Use Rules to create a custom rule to disallowing 'edit' for nodes that have price offers (= were flagged). This rule is a variation of the rule I included (in export format) in my answer to the question about How to restrict access to a node via node/12 and allow access via a path like content/sometitle?

These are the changes to that rule to make it work this case also:

• The paths containing node should be extended by adding /edit at the end (I'm assuming that's how the URL for your edit link looks like).
• Add a Rules Condition to check if the node was flagged (with the flag from step 1).
• Change the "Message" in the Rules Action to something to indicate that the edit is not allowed because it already has price offers.
• Modify the Rules Action to fit your own requirements, e.g. to issue a redirect to some 'help page' with more details about this.

If you've problems adding the appropriate Rules Conditions (to find the relevant data selector), it might be because of what's mentioned in the Rules UI when you're adding a "data comparison" condition: somewhere it says "The data selector helps you drill down into the data available to Rules. To make entity fields appear in the data selector, you may have to use the condition 'entity has field' (or 'content is of type')".

Remark: this will block edits from anybody. Should you only want to block that for the node author, then (in step 3) add an extra Rules Condition to verify if the currently logged on user matches the node author. Variation of this could be that you want to allow such edits anyhow for some selected roles (by adding an appropriate Rules Condition to verify the role of the current user).

Answer 3

I'd propose to not even show the edit link anymore if the user is not allowed to edit it. It is bad user experience to have a user click a button and then tell him he is not supposed to be there.

Drupal has an excellent content control system which you can use. It does involve some coding (< 20 lines), but I guess the result will be better than the other answers here.

You will have to create a custom module (a small one). Read that tutorial for information on creating a mymodule.info file.

Also create a mymodule.module file and implement hook_node_access:

function mymodule_node_access($node, $op, $account) {
  // If this user is the node author and he wants to edit a node?
  if ($account->uid == $node->uid && $op == 'update') {
    // Get comment count
    $comment_count = db_query('SELECT COUNT(cid) AS count FROM {comment} WHERE nid = :nid', array(':nid' => $node->nid))->fetchField();
    // If there is 1 comment or more
    if ($comment_count > 0) {
      // Deny the user access (and hide the edit link).
      return NODE_ACCESS_DENY;
    }
  }
  return NODE_ACCESS_IGNORE;
}

That is all you need to put in this file. It allows admins and other privileged user to still edit the node (remove the $account->uid == $node->uid && part if you want to block those as well).

So you need only two files and a folder and this is in my opinion more user friendly than giving the user the impression he can edit something and then tell him he cannot.

An optional addition can be to show a message that the user can no longer edit the node during the viewing. Add this to the module file:

function mymodule_node_view($node, $view_mode, $langcode) {
  // Fetch the current user.
  global $user;

  // Compare
  if ($user->uid == $node->uid) {
    // Get comment count
    $comment_count = db_query('SELECT COUNT(cid) AS count FROM {comment} WHERE nid = :nid', array(':nid' => $node->nid))->fetchField();
    // If there is 1 comment or more
    if ($comment_count > 0) {
      // Show the message
      drupal_set_message(t('This enquiry has received at least one price offer an can no longer be edited.'), 'warning');
    }
  }
}