[NSNull length]: unrecognized selector sent to instance in objective-c [duplicate] - ios

Question

This question already has answers here:
[NSNull isEqualToString:]
(7 answers)
Closed 6 years ago.
I am getting some JSON data from a service, one property is a string to represent an image url, it seems what is returned is NULL, I do the check but XCode breaks before my if statement and generate an exception. this is my code below:
- (void)configureCellForAlbum:(Album *)album {
self.albumTitle.text = album.albumTitle;
self.artisteName.text = album.artisteName;
NSURL *imageUrl = [NSURL URLWithString:album.thumbnail];
if (imageUrl == nil) {
self.albumThumbnail.image = [UIImage imageNamed:#"music_record"];
}
else {
self.albumThumbnail.imageURL = imageUrl;
}
}
the exception is
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull length]: unrecognized selector sent to instance.
How do I do the check so that if the value retured is null, it uses a local image but if not null to use the image string url that is returned?

Answer 1

nil is returned by the dictionary if no object with that key was found.
An instance of NSNull is inserted by the JSON parser to indicate that a null-valued key was present.
You need to check whether the object you got back was really a string. You are failing to catch the case where there is an object but it is not a string.
E.g.
if ([albm.thumbnail isKindOfClass:[NSString class]])
... a string-form URL is present ...
else
.... something else, or nothing, was found; use a fallback ...

Answer 2

I tried from other question which asked same that what you ask here.But you need to customize the code like above Tommy's code.
NSDictionary *dict = [[NSDictionary alloc]initWithObjectsAndKeys:#"iOS",#"language",nil];
id Value = [dict objectForKey:#"language"];
NSString *strLanguage = #"";
if (Value != [NSNull null]) {
strLanguage = (NSString *)Value;
NSLog(#"The strLanguage is - %#", strLanguage);
}
Output
The strLanguage is - iOS
Thank You nhgrif:-)