objective c - NSNotification arrived with broken object -

i'm posting notification in manner:

... ivsession *newsession = [[[ivsession alloc] initwithdictionary:propertydict] autorelease];       nsdictionary *notifparams = [nsdictionary dictionarywithobject:newsession  forkey:@"session"];         nsnotification *newsessionnotif = [nsnotification notificationwithname:ivnewsessionnotificaiton object:self userinfo:notifparams];  ... 

ivsession interface:

@interface ivsession : ivmappableobject {     nsstring *_ssid;     nsnumber *_uid;     }  @property (nonatomic,retain) nsstring *sessionid; @property (nonatomic,retain) nsnumber *userid; 

and init method:

- (id)initwithdictionary:(nsdictionary*)dict {     if ((self = [super init]))     {         nsdictionary *mapping = [self elementtopropertymappings];         (nsstring *key in mapping)             [self setvalue:[dict objectforkey:key] forkey:[mapping objectforkey:key]];     }         return self; } 

but @ method, called notification, i'm receiving broken newsession object - properties ssid , uid invalid summaries:

-(void)didopensession:(nsnotification *)newsession {     if (receivedsession)         [receivedsession release];     receivedsession =  [[newsession userinfo] objectforkey:@"session"]; }  

where fault?

code looks ok me... have verified ivsession object contains expect to, after assembling things, prior posting notification?