# objc_getClassList(_:_:) Obtains the list of registered class definitions. ``` func objc_getClassList(_ buffer: AutoreleasingUnsafeMutablePointer?, _ bufferCount: Int32) -> Int32 ``` ## Parameters `buffer` An array of `Class` values. On output, each `Class` value points to one class definition, up to either `bufferCount` or the total number of registered classes, whichever is less. You can pass `NULL` to obtain the total number of registered class definitions without actually retrieving any class definitions. `bufferCount` An integer value. Pass the number of pointers for which you have allocated space in `buffer`. On return, this function fills in only this number of elements. If this number is less than the number of registered classes, this function returns an arbitrary subset of the registered classes. ## Return Value An integer value indicating the total number of registered classes. ## Discussion The Objective-C runtime library automatically registers all the classes defined in your source code. You can create class definitions at runtime and register them with the `objc_addClass` function. The code listing below demonstrates how to use this function to retrieve all the class definitions that have been registered with the Objective-C runtime in the current process. ```objc int numClasses; Class * classes = NULL; classes = NULL; numClasses = objc_getClassList(NULL, 0); if (numClasses > 0 ) { classes = malloc(sizeof(Class) * numClasses); numClasses = objc_getClassList(classes, numClasses); free(classes); } ``` ### Special Considerations You can’t assume that class objects you get from this function are classes that inherit from [`NSObject`](/documentation/ObjectiveC/NSObject-swift.class), so you can’t safely call any methods on such classes without detecting that the method is implemented first. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)