Objective c nil vs null

Beware that if [NSNull null] returns true. They both are just typecast zero's. Functionally, there's no difference between them. One more thing nil is an object value while NULL is a generic pointer value. To expand on a comment from cobbal: MacTypes. Continue Reading. How to determine if variable is 'undefined' or 'null'? C represents nothing as 0 for primitive values and NULL for pointers which is equivalent to 0 in a pointer context.

Although semantically distinct from NULL , they are technically equivalent. Perhaps the most notable behavior of nil , however, is that it can have messages sent to it without a problem.

In other languages, like Java, this kind of behavior would crash your program. It makes complete sense if you think about it. Earlier we said NSNull is a placeholder for actual nothingness, and if you want a dictionary that can have nothingness, you need to use a placeholder for nothingness.

This has been the source of many weird crashes for the following reason: In Objective-C, you can send messages to nil , but when you are sending messages to a real object, the object needs to implement the method you want to call - in other words, you want the object to respond to a selector. To clarify the following point, we will try to print the contents of the Nendoroid key, and the dolls in the HarmoniaBloom key, using for in.

Behind the scenes, for-in will call the countByEnumeratingWithState:objects:count: method in arrays. The key does not exist in the dictionary at all:. On the other hand, trying to print the contents of the HarmoniaBloom array will have unexpected consequences:.

On the other hand, when we access an existing key whose value is NSNull , the program will crash, because NSNull is an object like any other, and it expects to receive selector calls that it can respond to. Failing to do so will cause your program to crash.

Therefore, when accessing dynamic dictionary data, you need to check if the object that will receive a selector is NSNull before you send any messages to it. Note : The sample code here omits working with optionals safely unless it is necessary for the example.

Always work with your optionals responsibly and avoid force-unwrapping optionals as much as possible. First, if you want to be as type safe as possible, you will likely want to cast the result of JSONSerialization. In this case:.

Using this, the parsing will succeed without an issue. Collectives on Stack Overflow. Learn more. Asked 12 years, 11 months ago. Active 5 years, 8 months ago. Viewed 94k times. Improve this question. Add a comment. Active Oldest Votes.

Improve this answer. VisioN k 29 29 gold badges silver badges bronze badges. Paul Tomblin Paul Tomblin k 56 56 gold badges silver badges bronze badges. I would think that to be a common case.

You can.