Set primary key when model's $useAutoIncrecement = false;

Thank you for your reply however it does not answer my question.

My table has a unique primary key, but there is no way to set that primary key if it is not an auto incteasement.

I need my primary key to a string, not ints.

Codeigniter says I am responsible to provide the correct and unique value for the key but i cant set it using the model.