Tukukkk

I am experimenting with metadata.

In this document :

https://www.dartlang.org/guides/language/language-tour#metadata

It is said that:

Metadata can appear before a library, class, typedef, type parameter,
constructor, factory, function, field, parameter, or variable
declaration and before an import or export directive. You can retrieve
metadata at runtime using reflection.

Thus... I try to get metadata...

// Resources:

// https://stackoverflow.com/questions/26826521/executing-bundle-of-functions-by-their-metadata-tag-in-dart-lang



import 'dart:mirrors';



/// This class represents the metadata "OnFailure".

class OnFailure {

  final int criticalityLevel;

  final String handlerName;

  /// Constructor.

  /// [criticalityLevel] represent the level of criticality.

  /// [handlerName] represents the name of the function to execute.

  const OnFailure(int this.criticalityLevel, String this.handlerName);

}



/// This class represents the metadata "Log".

class Log {

  final String destination;

  const Log(String this.destination);

}



/// This class represents the metadata "Doc".

class Doc {

  final String path;

  const Doc(String this.path);

}



@OnFailure(0, 'onFatalHandler')

class ClassProcessor {

  @Doc('/var/doc/ClassProcessor')

  bool status;



  @Log('/var/log/ClassProcessor')

  bool call(int value) {

    return value > 0;

  }

}



@OnFailure(0, 'onFatalHandler')

typedef bool TypeProcessor(int value);



main() {



  ClassProcessor processorClass = ClassProcessor();



  // Get the metadata for a class.

  InstanceMirror instanceMirror = reflect(processorClass);

  ClassMirror classMirror = instanceMirror.type;

  print(instanceMirror.type.metadata); // => [InstanceMirror on Instance of 'OnFailure']

  OnFailure metadata = classMirror.metadata[0].reflectee;

  print("Critical level: ${metadata.criticalityLevel}"); // => Critical level: 0

  print("Handler name: ${metadata.handlerName}"); // => Handler name: onFatalHandler



  // Get the metadata for a method.

  MethodMirror methodMirror = classMirror.declarations[Symbol('call')];

  Log log = methodMirror.metadata[0].reflectee;

  print("Log file is ${log.destination}");



  // Get the metadata for a property.

  VariableMirror variableMirror = classMirror.declarations[Symbol('status')];

  Doc doc = variableMirror.metadata[0].reflectee;

  print("Doc file is ${doc.path}");



  // Get the metadata for a typedef.

  // ???

  TypeProcessor processorInstance = (int value) {

    if (value > 0) {

      print("That's OK.");

    } else {

      print("A fatal error occurred !");

    }

  };



  instanceMirror = reflect(processorInstance);

  instanceMirror.type.declarations.forEach((Symbol symbol, DeclarationMirror declarationMirror) {

    print(declarationMirror.metadata);

  });



  // Get the metadata for a variable.

  // ???

  @Doc('/var/doc/data')

  int data = 10;



  instanceMirror = reflect(data);

  print(instanceMirror.reflectee); // => 10

  instanceMirror.type.declarations.forEach((Symbol symbol, DeclarationMirror declarationMirror) {

    print(declarationMirror.metadata);

  });

}

I can get metadata for classes, class properties and class methods, but I can't do so with "typedef" and for a variable.

Any idea on how to get metadata for anything other than a class or a class member ?

This seems to be a Dart bug.

With

  var mirrorSystem = currentMirrorSystem();

  var libraryMirror = mirrorSystem.libraries.keys

      .where((k) => k.path.endsWith('/bin/main.dart'))

      .map((k) => mirrorSystem.libraries[k])

      .first;

libraryMirror.declarations should include typedefs, but it doesn't.