CODEWITHSUNDEEP
iphoneobjective-ciosxcode
Richard Knop
Richard Knop

Reputation: 83755

How to check if value in array is not NULL?

So I am parsing a twitter timeline. There is a field called "following" in the JSON response. It should be true or false.

But sometimes the field is missing.

When I do:

NSLog(@"%@", [[[timeline objectAtIndex:i] objectForKey:@"user"] objectForKey:@"following"]);

This is the output:

1
1
0
0
1
<null>
1
1

So how to check for those values?

Upvotes: 3

Views: 5489

Answers (4)

Vineesh TP
Vineesh TP

Reputation: 7973

for checking array contain null value use this code.

if ([array objectAtIndex:0] == [NSNull null])
{
//do something
}
else
{
}

Upvotes: -1

Lee Fastenau
Lee Fastenau

Reputation: 444

It's not the timeline element that's null. It's either the "user" dictionary or the "following" object that's null. I recommend creating a user model class to encapsulate some of the json/dictionary messiness. In fact, I bet you could find an open source Twitter API for iOS.

Either way, your code would be more readable as something like:

TwitterResponse *response = [[TwitterResponse alloc] initWithDictionary:[timeline objectAtIndex:i]];
NSLog(@"%@", response.user.following);

TwitterResponse above would implement a readonly property TwitterUser *user which would in turn implement NSNumber *following. Using NSNumber because it would allow null values (empty strings in the JSON response).

Hope this helps get you on the right track. Good luck!

Upvotes: -1

Roy
Roy

Reputation: 3634

NSArray and other collections can't take nil as a value, since nil is the "sentinel value" for when the collection ends. You can find if an object is null by using:

if (myObject == [NSNull null]) {
    // do something because the object is null
}

Upvotes: 13

joerick
joerick

Reputation: 16468

If the field is missing, NSDictionary -objectForKey: will return a nil pointer. You can test for a nil pointer like this:

NSNumber *following = [[[timeline objectAtIndex:i] objectForKey:@"user"] objectForKey:@"following"];

if (following)
{
    NSLog(@"%@", following);
}
else
{
    // handle no following field
    NSLog(@"No following field");
}

Upvotes: 3

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