Check if property of object instance is 'blank'

I am trying to implement the code below without success. Basically, I want to set the display name to use thisPhoto.userFullName if it is not 'Blank", else show thisPhoto.userName instead.

UILabel *thisUserNameLabel = (UILabel *)[cell.contentView viewWithTag:kUserNameValueTag];

NSLog(@"user full name %@",thisPhoto.userFullName);
NSLog(@"user name %@",thisPhoto.userNam开发者_开发问答e);
if (thisPhoto.userFullName && ![thisPhoto.userFullName isEqual:[NSNull null]] ) 
{
   thisUserNameLabel.text = [NSString stringWithFormat:@"%@",thisPhoto.userFullName];
}
else if (thisPhoto.userFullName == @"")
{
   thisUserNameLabel.text = [NSString  stringWithFormat:@"%@",thisPhoto.userName];
}

Currently, even if userFullName is blank, my userName is still not displayed on the screen.

I'd prefer

if([thisPhoto.userFullName length])

Use -length. This will be 0 whenever the string is nil or the empty string @"". You generally want to treat both cases identically.

NSString *fullName = [thisPhoto userFullName];
thisUserNameLabel.text = [fullName length]? fullName : [thisPhoto userName];

I see a few points here

First - if your userFullName instance variable is NSString* then doing simple comparison with nil is enough:

if (thisPhoto.userFullName)

Unless, of course, you explicitly set it to be [NSNull null], which then requires the condition you wrote.

Second - comparing strings is done with isEqualToString: method so second condition should be rewritten as:

if ([thisPhoto.userFullName isEqualToString:@""]) {
    ...
}

Third - there's logic flaw - If your userFullName IS equal to empty string (@"") the code would still fall to the first branch. I.e. empty string (@"") is not equal to [NSNull null] or simple nil. Hence you should write to branches - one to handle empty string and nil, other one for normal value. So with a bit of refactoring your code becomes like this:

thisUserNameLabel.text = [NSString stringWithFormat:@"%@",thisPhoto.userFullName];
if (!thisPhoto.userFullName || [thisPhoto.userFullName isEqualToString:@""]) {
    // do the empty string dance in case of empty userFullName.
}

If, as I suppose, thisPhoto.userFullName is a NSString you may try

[thisPhoto.userFullName isEqualToString:@""]

The other two answers are correct, and beat me to it. Rather than just repeat what they have said - I'll point out something else.

[NSNull null] is used to store nil values in collection classes (NSArray, NSSet, NSDictionary) that don't allow nil values to be stored in them.

So unless you're checking values that you get from a collection - there is no point checking against [NSNull null]

// this assumes userFullName and userName are strings and that userName is not nil
thisUserNameLabel.text = [thisPhoto.userFullName length] > 0 ? thisPhoto.userFullName : thisPhoto.userName;

"Blank" means @"", but also @" " or @"\n". So I would trim userFullName and check the length of that string.

if ([[thisPhoto.userFullName stringByTrimmingCharactersInSet:
        [NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0) {

    // it's blank!
}