| # Errors in FFIgen | |
| This file documents various errors and their potential fixes related to FFIgen. | |
| ## Errors in source header files | |
| FFIgen uses libclang to parse header files. Any compiler warnings/errors should be logged (with SEVERE level). | |
| Compiler errors and warnings should be resolved as they can potentially generate invalid bindings that might cause silent errors and crashes at runtime. | |
| > You can pass in args to libclang using `compiler-opts` via cmd line or yaml config or both. | |
| Here we'll list some common usecases. You can find the full list of [supported args here](https://clang.llvm.org/docs/ClangCommandLineReference.html#id5). | |
| ### Missing headers | |
| These are the most common source file errors. You can specify [include paths to clang](https://clang.llvm.org/docs/ClangCommandLineReference.html#id6) like this | |
| ```yaml | |
| compiler-opts: | |
| - "-I/path/to/folder" | |
| ``` | |
| ### Ignoring source errors | |
| As a last resort, you can pass in `--ignore-source-errors` or set `ignore-source-errors: true` in yaml config. | |
| **Warning: This will likely lead to incorrect bindings!** | |
| ## Errors in Objective-C bindings | |
| ### Method not defined | |
| ObjC's method naming is a bit different to Dart's. For example, `NSString` has | |
| a method `stringWithCharacters:length:`. To make invocation feel as similar to | |
| ObjC as possible, we generate this as a method named `stringWithCharacters`, | |
| with a named required parameter called `length`. | |
| So one reason you might be having trouble invoking the method is that this | |
| naming convention is different to ObjC. The generated methods have a comment | |
| giving their full ObjC name, so you can try searching for that string to find | |
| the corresponding Dart method. | |
| Since Dart doesn't support method overloading, the method may have been renamed | |
| to avoid collisions. Again the best approach is to search for the ObjC method | |
| name. | |
| When FFIgen generates bindings for an ObjC interface, eg `Foo`, it generates a | |
| Dart class `Foo`, which contains the constructor and static methods. The | |
| instance methods are generated in an extension, `Foo$Methods`. | |
| So if you've searched for the generated method and found it, and still can't | |
| invoke it, it's possible that you've imported the class, `Foo`, but not the | |
| extension `Foo$Methods`. This can happen if you're using `show`/`hide` when you | |
| import the bindings. Make sure to import both `Foo` and `Foo$Methods`. |