| [](https://github.com/dart-lang/native/actions/workflows/objective_c.yaml) |
| [](https://coveralls.io/github/dart-lang/native?branch=main) |
| [](https://pub.dev/packages/objective_c) |
| [](https://pub.dev/packages/objective_c/publisher) |
| |
| # objective_c |
| |
| A library to access Objective C from Flutter that acts as a support library for |
| package:ffigen. |
| |
| This library isn't very useful on its own. Typically it is used while |
| interoperating with an Objective C library created by package:ffigen. See |
| https://pub.dev/packages/ffigen |
| |
| For general information about interop with Objective C, see |
| https://dart.dev/guides/libraries/objective-c-interop |
| |
| ## Memory management |
| |
| Objective C and Dart use different styles of memory management. Dart is garbage |
| collected, while Objective C uses reference counting. This difference is a |
| common cause of bugs when interoperating between the two languages. |
| |
| Memory management issues typically manifest as seg faults, which can be hard to |
| debug as they often have no useful stack trace. The most common issue is use |
| after free errors, where a Dart object is constructed to wrap an Objective C |
| object that has already been destroyed. To debug these issues, try running your |
| program with [asserts enabled](https://dart.dev/language/error-handling#assert). |
| When the Dart wrapper object is created or destroyed, an assert checks that the |
| Objective C object still exists, which should provide a much more useful stack |
| trace. |
| |
| References are automatically retained when the Dart wrapper object is |
| created, and released when the Dart object is garbage collected. But to fix a |
| reference counting issue, it may occasionally be necessary to manually control |
| the ref count. The ref count of the Objective C object can be controlled from |
| Dart by the `retain` and `release` options in the Dart wrapper object |
| constructors, and by the `retainAndReturnPointer()` and `release()` methods. |
