Getting rev from DBFILESMetadata in obj-c API 2

Dear Dropbox,

Thanks for the new obj-c API v2, looks like quite an effort! So far it's more convenient to use than API v1 and integration is going well. However, I'm a little held up on how to work with the response objects, I'm constantly looking for methods and properties on them that don't seem to be there and I think I'm misunderstanding how the union and struct object types work, the response and error objects. Here's a small example: I'm checking that a file exists, and in API v1 I hung on to the `rev` of the file, so that after I download it and modify it, I want to push it back up, and I need the rev on upload to do that without creating a new file/conflict.

According to this thread you can get the rev from the DBFILESMetadata response object in API 2:

https://www.dropboxforum.com/t5/API-support/Using-file-revs-in-API-2/m-p/191299#M8348

> In API 2, DBFILESFileMetadata has an equivalent .rev property - so far, so good.

But I'm pretty baffled as to where/how, I don't see it any such property listed for that object in the docs:

https://dropbox.github.io/dropbox-sdk-obj-c/api-docs/latest/Classes/DBFILESMetadata.html

Here's a simple request that I think helps lay out where I'm getting confused:

[[client.filesRoutes getMetadata:path] response:^(DBFILESMetadata * _Nullable result, DBFILESGetMetadataError * _Nullable routeError, DBError * _Nullable error) {
    if (result != nil) {
        // File exists at that path
        self.foundFile = YES;
        // save the file rev
        self.dropboxFileRevsion = ... ?
    } else {
        self.foundDatabaseFile = NO;
        // But how do I check DBFILESGetMetadataError correctly for this request
        // to see if it's file not found—or some other error? I can't tell from
        // docs just yet
        if (routError != nil) {
        	// the only property on routeError that seems to relate is path...
        }
    }
    [self doNextThing];
}];

Thanks for your time!