Using Custom Fields to Trigger Specific Actions on Saving a Post?

Question

Can custom fields be used to determine specific actions upon saving a post to the database?

Which action(s) make this possible, since adding post medata seems to always occur after saving a post and thus any plugin hooking into wp_insert_post is activated before the post meta data has been added to the post.

Answer 1

If you are wanting to run the function after the post meta data has been added/updated, use:

add_action( 'updated_post_meta', 'my_post_meta_function' );

Answer 2

If there's no complicated logic involved in updating the custom fields, you could derive the new values by grabbing their (changed) values from $_POST and combining these with their existing values from the database. Base your processing upon the resulting values.