Convert NSNumber to int in Objective-C

Question

I use [NSNumber numberWithInt:42] or @(42) to convert an int to NSNumber before adding it to an NSDictionary:

int intValue = 42;
NSNumber *numberValue = [NSNumber numberWithInt:intValue];
NSDictionary *dict = @{ @"integer" : numberValue };

When I retrieve the value from the NSDictionary, how can I transform it from NSNumber back to int?

NSNumber *number = dict[@"integer"];
int *intNumber = // ...?

It throws an exception saying casting is required when I do it this way:

int number = (int)dict[@"integer"];

Hammertoe

Answer 1

Have a look at the documentation. Use the intValue method:

NSNumber *number = [dict objectForKey:@"integer"];
int intValue = [number intValue];

Nazi

Implicit conversion is now disallowed with ARC. – Physics

basically [key intValue] (key is NSNumber) – Descartes

Answer 2

You should stick to the NSInteger data types when possible. So you'd create the number like that:

NSInteger myValue = 1;
NSNumber *number = [NSNumber numberWithInteger: myValue];

Decoding works with the integerValue method then:

NSInteger value = [number integerValue];

Raft

Why should he stick to the NSInteger? – Fitzhugh

NSInteger is a primitive type thats much faster during execution that NSNumber which is an object. – Raft

And what is int? A primitive too? – Fitzhugh

int is primitive too, yes. However it's maximum allowed number is less precisely defined. NSInteger is essentially just an alias to some primitive integer type that's known to be 32bit on 32bit machines and 64bit on 64bit devices. – Raft

So it's a good idea to use NSInteger over int in the most cases? – Fitzhugh

Yes, Apple suggests to. – Raft

Seelmann, but I guess that if I know the numbers I need are not large, it's ok to use int over NSInteger, right? – Fitzhugh

I'd recommend not guesstimating anything about native number arithmetics. You can sure use int, but there is little point in doing so, except for interfacing with cross-platform libs. And even then something like uint32_t would be better to use. – Raft

I'm sorry if I'm bothering you, I'm just trying to learn and understand more. I recently started learning Objective C working on a big project and I'm thinking about ways to refactor it. So, it's a good idea to replace int with NSInteger everywhere possible in the existing project, right? – Fitzhugh

Doing that would certainly make it more consistent with platform coding standards, yes. – Raft

Always use NSInteger. – Striker

Answer 3

Use the NSNumber method intValue

Here is Apple reference documentation

Accidental

Answer 4

A less verbose approach:

int number = [dict[@"integer"] intValue];

Panocha

Answer 5

A tested one-liner:

int number = ((NSNumber*)[dict objectForKey:@"integer"]).intValue;

Riba