mirror_dispatcher 1.0.1

Method Dispatcher using dart:mirrors. Facilitates invoking an API for JSON-RPC server side implementation.

MirrorDispatcher implements [Dispatcher] by introspecting a class instance using [dart:mirrors]. dart:mirrors allows you to invoke an instance's methods by their string names.

Construct a [MirrorDispatcher] with a class instance. MirrorDispatcher.dispatch("someMethod") will return a Future of whatever value it returns.

This is for JSON-RPC, so there are some restrictions. A method can only be invoked with positional or named parameters, not both. Optional parameters should work as expected.

MirrorDispatcher is mainly a wrapper around dart:mirrors. For any method dispatched, Dispatcher returns either the return value of the method or instances of one of three "Exception" classes. Most errors will be corralled into these objects, so that runtime exceptions don't get thrown, instead are returned in an orderly manner.

Usage

A simple usage example:

import 'package:mirror_dispatcher/mirror_dispatcher.dart';

/// Look in test/mirror_dispatcher_test.dart for additional examples.

/// Make a class with the API we want. Something silly but instructive.
///
/// Hold count in Foo.
class Foo {
  num _count = 0;

  /// initialize with a count
  Foo(this._count);

  /// increment with an optional positional parameter
  void increment([num aNumber = 1]) => _count += aNumber;

  /// decrement with a required named parameter
  void decrement({required num aNumber}) => _count -= aNumber;

  /// get the current value of count
  num getCount() => _count;

  /// we decrement by 2 a lot.
  num goTwoLess() {
    _count -= 2;
    return _count;
  }
}

void main() async {
  /// make a dispatcher with an initialized instance of Foo class
  var dispatcher = MirrorDispatcher(Foo(29));

  /// dispatch a method with a parameter
  await dispatcher.dispatch('increment', 4);

  /// get the new value
  var c = await (dispatcher.dispatch('getCount'));
  printCount(c); // 33

  /// dispatch a method with a named parameter
  await dispatcher.dispatch('decrement', {'aNumber': 18});
  var d = await (dispatcher.dispatch('getCount'));
  printCount(d); // 15

  /// dispatch a method without a parameter
  await dispatcher.dispatch('increment');
  var e = await (dispatcher.dispatch('getCount'));
  printCount(e); // 16

  var f = await dispatcher.dispatch('goTwoLess');
  printCount(f); // 14
}

void printCount(num aCount) {
  print('the currentCount is $aCount');
}

Features and bugs

Please file feature requests and bugs at the issue tracker.