This morning, I had one of my d'oh moments: finally figuring out exactly how to do inter-app copy and paste without breaking SDK rules. It basically goes like this, in a similar fashion to the Core Location service I wrote about a few months ago:

To make copy/paste work, you need to install a central application. I'm going to call it "CopyPasteOMatic" for no particularly good reason. It has a custom URL scheme, cpomatic://. You can call it in one of two ways, either as a paster or a pastee.

Each client on the iPhone must supply its own custom URL scheme, and pass it when calling CopyPasteOMatic. For example, scheme=vnotes lets CPOmatic know who to return the data to.

Clients need to pass an operation as well, either op=copy or op=paste. There's no need to specify whether a paste should be public or private because all pastes are public, but it might help to paste with a key though, allowing developers to put application-specific data into a public mailbox that can be consumed by other apps regardless of the system clipboard.

Should security be an issue, I think it would be possible to issue public and private keys that authenticate the copy or paste request, so developers can control where their data is allowed to go. The drawback of that would be that CopyPasteOMatic would have to call home every now and then to download and store those keys in the local keychain.

As for the data itself, that could be posted in URI-encoded strings attached to the URLS, going into or out of the paste service. The obvious drawback is going to be length. I'm unsure as to how long a URL the iPhone will permit to be opened between applications.

Anyway, so that's the idea in a nutshell: a community developed central cut/paste application and a well-defined protocol to support it. How much would you like to bet that it would never get accepted into AppStore?