NSOPTIONS

NS_OPTIONS is a macro used in Objective-C to declare bitmask-based option sets. It defines a new, strongly-typed unsigned integer type whose values are intended to be combined with bitwise operations. The macro helps create a collection of independent flags that can be stored in a single variable and tested efficiently.

Typically, NS_OPTIONS is used like this:

typedef NS_OPTIONS(NSUInteger, MyOptions) {

MyOptionFirst = 1 << 0,

MyOptionSecond = 1 << 1,

MyOptionThird = 1 << 2

};

A variable of type MyOptions can hold any combination of these flags. For example:

MyOptions options = MyOptionFirst | MyOptionSecond;

if (options & MyOptionFirst) {

// handle first option

}

Checking for a specific flag is usually done with a bitwise AND operation.

Swift interoperability treats NS_OPTIONS as a bridged type that maps to the Swift OptionSet protocol, enabling Swift code to express combinations with a concise syntax such as [.MyOptionFirst, .MyOptionSecond].

NS_OPTIONS is contrasted with NS_ENUM, which defines a plain enumeration where only one value is expected at a time. NS_OPTIONS is specifically intended for bitmasks where multiple options may be enabled simultaneously.

Originating in Apple’s Cocoa and Cocoa Touch frameworks, NS_OPTIONS is commonly used to configure behavior or capabilities, such as animation options, layout preferences, or feature flags. While the macro is most associated with Objective-C, its concept—typed bitmasks—remains a foundational pattern across Apple platforms.