NSUInteger

NSUInteger is an unsigned integer type used in Apple's Cocoa and Cocoa Touch frameworks. It is the standard type for representing counts, lengths, and indices in APIs such as NSArray, NSString, NSData, and NSRange. The exact size of NSUInteger depends on the platform: it is 32 bits on 32-bit environments and 64 bits on 64-bit environments.

In Apple's headers, NSUInteger is typically defined as an unsigned long (typedef unsigned long NSUInteger). Because its size follows the platform’s pointer width, code that uses NSUInteger can scale naturally between 32- and 64-bit targets. As an unsigned type, it cannot represent negative values, which makes it suitable for counts and array indices where negative numbers would be invalid.

Many APIs use NSUInteger for return values that indicate positions or lengths. A common sentinel value in such contexts is NSNotFound, which is used to indicate “not found” or an invalid index; NSNotFound is defined as a large integer (NSIntegerMax) and can be assigned to or compared with an NSUInteger when appropriate.

In Swift, NSUInteger is imported as UInt, reflecting the same unsigned, platform-dependent size semantics. When writing Swift code, developers often prefer the native Int or UInt types for clarity, but bridging with Objective-C APIs that use NSUInteger remains seamless.

See also: NSInteger, NSNotFound, NSUInteger constant, and API guidelines for counts and indices.