Add _Nullable to XMPPRoster

[alessioarsuffi]

Add _Nullable to method of XMPPRoster:

(NSArray *)jidsForXMPPStream:(XMPPStream * _Nullable)stream

to be able to call this from swift with a nil stream reference.

This is especially useful when user wants to retrieve roster from swift code and stream is not yet connected.

[alessioarsuffi]

Hi @chrisballinger :)

This is a small change to better support swift.
Please let me know if this is ok for you, i'm available to add more _Nullable flags to the framework in future.

Thanks

[chrisballinger]

I'm not sure if we really want to change this API contract. You can always construct an XMPPStream that is not connected and pass that in.

[alessioarsuffi]

- (NSArray *)jidsForXMPPStream:(XMPPStream * _Nullable)stream {
    
    XMPPLogTrace();
    
    __block NSMutableArray *results = [NSMutableArray array];
	
	[self executeBlock:^{
		
		NSManagedObjectContext *moc = [self managedObjectContext];
		
		NSEntityDescription *entity = [NSEntityDescription entityForName:@"XMPPUserCoreDataStorageObject"
												  inManagedObjectContext:moc];
		
		NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
		[fetchRequest setEntity:entity];
		[fetchRequest setFetchBatchSize:self->saveThreshold];
		
		if (stream)
		{
			NSPredicate *predicate;
			predicate = [NSPredicate predicateWithFormat:@"streamBareJidStr == %@",
                         [[self myJIDForXMPPStream:stream] bare]];
			
			[fetchRequest setPredicate:predicate];
		}
		
		NSArray *allUsers = [moc executeFetchRequest:fetchRequest error:nil];
        
        for(XMPPUserCoreDataStorageObject *user in allUsers){
            [results addObject:[user.jid bareJID]];
        }
		
	}];
    
    return results;
}

The problem is inside this method, if we use a not connected stream, will be applied to predicate a nil streamBareJidStr value, resulting in 0 fetched jabbers from database, if we pass a stream which is nil and not connected we will fetch jabbers from roster even if we are still not connected.
Without _Nullable in that signature is not possible to fetch jabbers from database without a valid stream connection. Because query will exclude all jabbers in roster.

Also, if stream cannot be nil, why we check if stream exist to create a predicate?

[chrisballinger]

@alessioarsuffi Sorry for the delay on this! An XMPPStream can be instantiated without being connected