DioError does not work with the new version of Dio:

1. "request" renamed to requestOptions
2. DioErrorType.RESPONSE -> DioErrorType.response

It is no good idea to use DioError in DataState I think. HTTP 403/404/500 etc.. is not a Dio error in fact.

Xcode's output: ↳ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/ffi-0.1.3/lib/src/utf8.dart:63:33: Error: The getter 'addressOf' isn't defined for the class 'Utf8'. - 'Utf8' is from 'package:ffi/src/utf8.dart' ('../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/ffi-0.1.3/lib/src/utf8.dart'). Try correcting the name to the name of an existing getter, or defining a getter or field named 'addressOf'. String toString() => fromUtf8(addressOf); ^^^^^^^^^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/ffi-0.1.3/lib/src/utf16.dart:16:7: Error: Struct 'Utf16' is empty. Empty structs and unions are undefined behavior. class Utf16 extends Struct { ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/ffi-0.1.3/lib/src/utf8.dart:23:7: Error: Struct 'Utf8' is empty. Empty structs and unions are undefined behavior. class Utf8 extends Struct { ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/sqlite3-0.1.8/lib/src/ffi/sqlite3.ffi.dart:14:7: Error: Struct 'sqlite3_context' is empty. Empty structs and unions are undefined behavior. class sqlite3_context extends Struct {} ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/sqlite3-0.1.8/lib/src/ffi/sqlite3.ffi.dart:12:7: Error: Struct 'sqlite3_value' is empty. Empty structs and unions are undefined behavior. class sqlite3_value extends Struct {} ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/sqlite3-0.1.8/lib/src/ffi/sqlite3.ffi.dart:10:7: Error: Struct 'sqlite3_stmt' is empty. Empty structs and unions are undefined behavior. class sqlite3_stmt extends Struct {} ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/sqlite3-0.1.8/lib/src/ffi/sqlite3.ffi.dart:8:7: Error: Struct 'sqlite3' is empty. Empty structs and unions are undefined behavior. class sqlite3 extends Struct {} ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/sqlite3-0.1.8/lib/src/ffi/sqlite3.ffi.dart:6:7: Error: Struct 'char' is empty. Empty structs and unions are undefined behavior. class char extends Struct {} ^ ../../development/flutter2.5.3/flutter/.pub-cache/hosted/pub.dartlang.org/ffi-0.1.3/lib/src/allocation.dart:47:33: Error: Expected type 'T' to be a valid and instantiated subtype of 'NativeType'. final int totalSize = count * sizeOf(); ^ Failed to package /Users/charlesyeh15/Downloads/flutter_clean_architecture-part3_local_data. Command PhaseScriptExecution failed with a nonzero exit code note: Using new build system note: Planning note: Build preparation complete note: Building targets in dependency order /Users/charlesyeh15/Downloads/flutter_clean_architecture-part3_local_data/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.2.99. (in target 'FMDB' from project 'Pods')

Could not build the application for the simulator. Error launching application on iPhone 8.

In the domain package you have some imports from the core package ( in usecases and repositories folders ). The main advantage of the hexagonal architecture is explicitly to avoid such imports. The problem here is that the ports aren't part of the domain but of the application layer ( core package ).