inherited_model_macro 0.1.0

Macro that generate boilerplate code for InheritedModel

Macro that generates boilerplate code for InheritedModel and simplifies state management

Usage can also be found in example.

All you need to do is declare class with fields (and methods to update values) and annotate it with @InheritedModelMacro():

 @InheritedModelMacro()
 class LogoModel extends InheritedModel<String> {
   final Color? backgroundColor; // nullable types are also supported in update methods
   final bool large;

   void toggleColor(BuildContext context) {
     final newValue = (backgroundColor == null) ? Colors.red : null;
     updateState(backgroundColor: newValue);
   }

   void toggleSize(BuildContext context) {
     updateState(large: large != true);
   }
 }

Then insert generated Holder class in a tree like Provider or InheritedWidget.

Scaffold(
   body: const LogoModelHolder(
     backgroundColor: Colors.blue,
     large: false,
     child: Content(),
 )

Notes:

• Your class MUST extends InheritedModel<String> until future versions when macros feature extendType stops breaking analyzer
• Dart sdk version must be ^3.5.0-152 or higher and macros must be enabled in analysis_options.yaml and during build (Documentation)
• Analyzer might throw errors that generated code is not there when applying macro on different projects, than macro itself (issue). Instead of working with code, that does not exist, you can try to dart unpack this package into your project

Generated code

Holder class

Your class

class LogoModel {
  // get field value
  static FieldType readField(context) 

  // get field value and subscribe to it's changes. When value changes, widget will be redrawn
  static FieldType watchField(context) 

  // find instance and update given fields
  static void update(context, fields?) 

  // update fields directly
  void updateState(fields?) 

  // get nearest instanse of class up in the tree
  static Type getInstance(context) 
}

Under the hood

Holder class provided setState callback to your class that updates values inside holder and provides them down to your class.

InheritedModel, like other InheritedWidgets, is needed for O(1) tree search. But it's marked @immutable, so all fields are supposed to be final and can't be changed -> are provided by holder.

Also InheritedModel is useful as it allows to separatly subscribe to changes of fields. This is done by passing field name as aspect to inheritFrom method. That is why your class must extend InheritedModel<String>.

Setting nullable fields are implemented by getting Object stub in case of passing nothing as default argument and comparing it to current field value.

The rest is basic InheritedModel boilerplate code.