Exploring Dart via the ERights money example

money.dart

// compare with https://bitbucket.org/DanC/coffee-craft/src/682d06f02e99/money.coffee

// ugh... no nested classes? gotta pass thunks around?
class SealedBox {
  final capture;
  SealedBox(this.capture);
  shareContent() { capture(); }
}

class Sealer {
  final save;
  Sealer(this.save);
  seal(it) => new SealedBox(() {save(it);});
}

class Unsealer {
  final flush;
  final bad;
  final fill;
  final extract;
  Unsealer(this.flush, this.bad, this.fill, this.extract);
  unseal(box) {
    flush();
    box.shareContent();
    if (bad())
      throw new IllegalArgumentException('invalid box');
    fill();
    flush();
    return extract();
  }
}

makeBrandPair(hint) {
  final noObject = new Object();
  var shared = noObject;
  var content = null;
  
  final sealer = new Sealer((it) {shared = it;});

  final unsealer = new Unsealer(
      () { shared = noObject;},
      () => shared == noObject,
      () { content = shared; },
      () => content );

  return [sealer, unsealer];
}

main() {
  // ugh... ;s everywhere
  print('eyeball-test makeBrandPair');
  // no destructuring assignment?
  final s_u = makeBrandPair('bob');
  final s = s_u[0];
  final u = s_u[1];
  final x = s.seal('abc');
  print(x);
  print(u.unseal(x));
}

/*
# connect the dots between node.js's console
# and http://wiki.erights.org/wiki/TextWriter
out = {
  print: (s) -> console.log(s)
}
*/