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# Objective-C Runtime

Gain low-level access to the Objective-C runtime and the Objective-C root types.

## Overview

The [`Objective-C Runtime`](/documentation/ObjectiveC) module APIs define the base of the Objective-C language. These APIs include:

- Types such as the ``doc://com.apple.objectivec/documentation/ObjectiveC/NSObject-swift.class`` class and the ``doc://com.apple.objectivec/documentation/ObjectiveC/NSObjectProtocol`` protocol that provide the root functionality of most Objective-C classes
- Functions and data structures that comprise the Objective-C runtime, which provides support for the dynamic properties of the Objective-C language

You typically don’t need to use this module directly.

## Topics

### Classes

[`NSObject`](/documentation/ObjectiveC/NSObject-swift.class)

The root class of most Objective-C class hierarchies, from which subclasses inherit a basic interface to the runtime system and the ability to behave as Objective-C objects.

[`Protocol`](/documentation/ObjectiveC/Protocol)

### Protocols

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

The group of methods that are fundamental to all Objective-C objects.

### Reference

[Objective-C Runtime](/documentation/ObjectiveC/objective-c-runtime)

Describes the macOS Objective-C runtime library support functions and data structures.

[Objective-C Structures](/documentation/ObjectiveC/objective-c-structures)

[Objective-C Constants](/documentation/ObjectiveC/objective-c-constants)

[Objective-C Functions](/documentation/ObjectiveC/objective-c-functions)

[Objective-C Data Types](/documentation/ObjectiveC/objective-c-data-types)

[Objective-C Macros](/documentation/ObjectiveC/objective-c-macros)

[Objective-C Enumerations](/documentation/ObjectiveC/objective-c-enums)


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