Mapping relationships to generic models in Datamapper for Codeigniter

Question

I have a number of different models in a system backed by the Datamapper library for Codeigniter such as Posts and Pages and am interested in adding Likes and Comments to the system. The way I see it, Likes and Comments can apply to any sort of model that extends Datamapper. How would I go about defining such a relationship (keep Likes for any sort of model in the same table, as well as Comments)?

Answer 1

I tend to create separate tables for likes and comments. I usually create this sort of schema:

Likes
-----
id      // autoincrement
obj     // the related model (the name of the model that is being liked)
obj_id  // the foreign key
user_id // the user id that liked the model object
created // timestamp
updated // timestamp

Then the comments table:

Comments
--------
id       // autoincrement
obj      // the related model (same as above)
obj_id   // the foreign key
message  // the comment itself
user_id  // the user id that commented on the model object
created  // timestamp
updated  // timestamp