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iOS Build a Simple iPhone App (iOS7) Creating a Data Collection Implementing an Array

Posted by malcolm parrish
malcolm parrish
2,093 Points

Why does the array have to end with nil?

No details

4 Answers

Alan Johnson
Alan Johnson
7,625 Points
Alan Johnson
Alan Johnson
7,625 Points

My understanding is that it's because Objective-C needs to know when the list ends for variable length arguments. I'm not sure why it can't detect it in its syntax, but it looks like that's the reason.

There's a interesting discussion here about it.

 Vladimir Cezar
 Vladimir Cezar
7,710 Points
 Vladimir Cezar
 Vladimir Cezar
7,710 Points

You can use a different syntax that does not require nil. Like so:

NSArray *arrayName = @[item1, item2, item3];

Stephen Whitfield
Stephen Whitfield
16,771 Points

Correct. This is called Objective-C Literals and is briefly covered here.

Michael Bowen
Michael Bowen
770 Points
Michael Bowen
Michael Bowen
770 Points

You need a nil because the pointer to the array points at the first element in the array and will keep traversing the array until it hits a nil, then it knows that is the end of the array.

If there is not a nil then the pointer will continue into arbitrary memory addresses.

This is the same concept of strings using null characters in C.

Shaun Kelly
Shaun Kelly
5,648 Points
Shaun Kelly
Shaun Kelly
5,648 Points

whats the difference between null and nill ?