In simple RESTful design, does PATCH imply mapping to CRUD's (ORM's) "update" and PUT to "destroy"+"create" (to replace a resource)?

Question

I'm trying to create a simple REST API and map it to CRUD. I have an ORM (DataMapper) which has methods like create, update and destroy.

If I get it right, given a resource {a:'foo',b:'bar',c:'baz'}, performing a PUT {b:'qux'} is supposed to replace the resource and result in the same {b:'qux'}, and doing a PATCH {b:'qux'} should result in {a:'foo',b:'qux',c:'baz'}.

Would PUT be implemented with ORM's destroy+create to completely recreate a database record (with the same old id) or both PUT and PATCH would be mapped to update (and only a record's fields would be manipulated)?

Answer 1

Well, Both the actions actually means update, where PUT is full update and PATCH is partial update. In case of PUT you already know the identifier of the resource and the resource already exists, so it is not a create and delete action per se. Infact, you can make do with providing only PUT action for your resource. The only idiosyncrasy of put is the client is supposed to provide full representation of resource. Since all request for put, must come after the GET of the resource, thus providing full representation shouldn't be problem for client anyway.

Answer 2

a) what PATCH does depends on the media type in the request. AFAIK, there is no definition for application/json, so you'd need to clarify that in the question.

b) both PUT and PATCH are update operations (with an optional create if the resource doesn't exist yet)