NS_ENUM & NS_OPTIONS

Introduced in Foundation with iOS 6 / OS X Mountain Lion, the NS_ENUM and NS_OPTIONS macros are the new, preferred way to declare enum types.

→ nshipster.com/ns_enum-ns_options/

NS_ENUM and NS_OPTIONS are the modern, Apple-approved way to declare enums and bit-masks.

NS_ENUM – for normal enumerated values

typedef NS_ENUM(NSInteger, UITableViewCellStyle) {
    UITableViewCellStyleDefault,
    UITableViewCellStyleValue1,
    UITableViewCellStyleValue2,
    UITableViewCellStyleSubtitle
};

• Gives a real, fixed-size type (here NSInteger)
• Compiler knows the type → better warnings, switch-statement checking
• Replaces the old “enum + separate typedef” pattern

NS_OPTIONS – for bitmasks

typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) {
    UIViewAutoresizingNone                 = 0,
    UIViewAutoresizingFlexibleLeftMargin   = 1 << 0,
    UIViewAutoresizingFlexibleWidth        = 1 << 1,
    UIViewAutoresizingFlexibleRightMargin  = 1 << 2,
    // …
};

• Same syntax as NS_ENUM, but tells the compiler values can be combined with |
• Enables bitwise operations with proper type safety

Rule of thumb

• Use NS_ENUM when only one value can be active (days of week, cell styles, etc.)
• Use NS_OPTIONS when multiple values can be combined (autoresizing masks, permissions, animation options, etc.)

Always prefer these macros over raw enum or old-style typedefs, they’re clearer, safer, and future-proof.