How can I check if an object in an NSArray is NSNull?

Question

I am getting an array with null value. Please check the structure of my array below:

 (
    \"< null>\"
 )

When I\'m trying to access

Answer 1

I found the code for working with NSNull has the following problems:

• Looks noisy and ugly.
• Time consuming.
• Error prone.

So I created the following category:

@interface NSObject (NSNullUnwrapping)

/**
* Unwraps NSNull to nil, if the object is NSNull, otherwise returns the object.
*/
- (id)zz_valueOrNil;

@end

With the implementation:

@implementation NSObject (NSNullUnwrapping)

- (id)zz_valueOrNil
{
    return self;
}

@end

@implementation NSNull (NSNullUnwrapping)

- (id)zz_valueOrNil
{
    return nil;
}

@end

It works by the following rules:

• If a category is declared twice for the same Class (ie singleton instance of the Class type) then behavior is undefined. However, a method declared in a subclass is allowed to override a category method in its super-class.

This allows for more terse code:

[site setValue:[resultSet[@"main_contact"] zz_valueOrNil] forKey:@"mainContact"];

. . as opposed to having extra lines to check for NSNull. The zz_ prefix looks a little ugly but is there for safety to avoid namespace collisions.