NS_ENUM vs enum - objective-c

Question

Objective C provides several ways to declare an enumeration. It could be declared via typedef enum or NS_ENUM. NS_ENUM macro takes type name as a parameter, and I do not completely understand its meaning. I didn't find description of NS_ENUM macro in official Apple documentation. What's a difference between using enum and NS_ENUM? And an other question if it's possible to use any other type in NS_ENUM instead NSInteger and its relative integer types?

Answer 1

NSHipster provided a very nice post that explains this thoroughly:
http://nshipster.com/ns_enum-ns_options/
To quote the bottom line:
This approach combines the best of all of the aforementioned approaches (enum, typedef enum), and even provides hints to the compiler for type-checking and switch statement completeness.

Answer 2

The main difference is that typedef NS_ENUM translates to a Swift enum properly, whereas typedef enum doesn't.

Answer 3

Here is the link to the official Apple's documentation:
https://developer.apple.com/library/content/releasenotes/ObjectiveC/ModernizationObjC/AdoptingModernObjective-C/AdoptingModernObjective-C.html#//apple_ref/doc/uid/TP40014150-CH1-SW6
From the subsection titled "Enumeration Macros":
The NS_ENUM and NS_OPTIONS macros provide a concise, simple way of defining enumerations and options in C-based languages. These macros improve code completion in Xcode and explicitly specify the type and size of your enumerations and options. Additionally, this syntax declares enums in a way that is evaluated correctly by older compilers, and by newer ones that can interpret the underlying type information.
Use the NS_ENUM macro to define enumerations, a set of values that are mutually exclusive:
typedef NS_ENUM(NSInteger, UITableViewCellStyle) {
UITableViewCellStyleDefault,
UITableViewCellStyleValue1,
UITableViewCellStyleValue2,
UITableViewCellStyleSubtitle
};
The NS_ENUM macro helps define both the name and type of the enumeration, in this case named UITableViewCellStyle of type NSInteger. The type for enumerations should be NSInteger.