--- title: "class_addIvar(_:_:_:_:_:)" framework: Objective-C Runtime role: symbol role_heading: Function platforms: [iOS 2.0+, iPadOS 2.0+, Mac Catalyst 13.1+, macOS 10.5+, tvOS 9.0+, visionOS 1.0+, watchOS 1.0+] path: "objectivec/class_addivar(_:_:_:_:_:)" --- # class_addIvar(_:_:_:_:_:) Adds a new instance variable to a class. ## Declaration ```swift func class_addIvar(_ cls: AnyClass?, _ name: UnsafePointer, _ size: Int, _ alignment: UInt8, _ types: UnsafePointer?) -> Bool ``` ## Return Value Return Value YES if the instance variable was added successfully, otherwise NO (for example, the class already contains an instance variable with that name). ## Discussion Discussion This function may only be called after objc_allocateClassPair(_:_:_:) and before objc_registerClassPair(_:). Adding an instance variable to an existing class is not supported. The class must not be a metaclass. Adding an instance variable to a metaclass is not supported. The instance variable’s minimum alignment in bytes is 1<