javascript - 如何在dart中编写on-*事件/回调注册

Question

我有一个包含一些事件的 JavaScript 类，我需要将其重写为 Dart。我不知道如何重写我们使用回调的部分。这是我的示例代码:

var Person = function (name) {
  this.name = name;
  this.onNameChangedCallbacks = [];
}

Person.prototype.onNameChanged = function(callback) {
  this.onNameChangedCallbacks.push(callback);
}

Person.prototype.setName = function (name) {
  this.name = name;
  this.onNameChangedCallbacks.forEach(function (callback){
    callback(name);
  });
}

var adam = new Person('Adam');

adam.onNameChanged(function(newName) {
  alert('New name is set to: ' + newName);
});

adam.setName('eva');

http://jsfiddle.net/R79Vy/

正如您所看到的，当名称更改时，所有注册的回调都会使用新的名称参数进行调用。你如何在 dart 中编写这段代码？谢谢

Answer 1

如果是自定义事件

elem.on['name-changed'].listen((e) {
  // handle event
});

如果是 DOM 事件，通常会有特定的 getter，例如

elem.onNameChanged.listen((e) {
  // handle event
});

// or

elem.onNameChanged.listen((e) =>  /* handle event (inline function body) */);

您还可以传递一个方法

elem.onNameChanged.listen(nameChangeHandler);

void nameChangeHandler(e) {
  // handle event
}

当你想明确取消订阅时(不依赖垃圾回收)

import 'dart:async';
StreamSubscription nameChangeSubscr;

nameChangeSubscr = elem.onnameChanged.listen((e) => /* handle event */);

// unsubscribe
if(nameChangeSubscr != null) nameChangeSubscr.cancel();

如果你想要像 DOM 事件这样的自定义事件的 getter How do I fire a custom event from Polymer Dart?

更新

也许这就是你想要的

import 'dart:async';

class Person {
  Stream onNameChange;
  //StreamController _controller = new StreamController();
  StreamController _controller = new StreamController.broadcast();
  Person() {
    onNameChange = _controller.stream;
  }

  String _name;
  String get name => _name;
  set name(String val) {
    _name = val;
    _controller.add(val);
  }
}

void main() {
  var p = new Person();
  StreamSubscriptions nameChangeSubscr = p.onNameChange.listen((e) => print('name changed: $e'));


  var i = 0;
  new Timer.periodic(new Duration(milliseconds: 300), (Timer t) {
    if(i > 5) {
      t.cancel();
      if(nameChangeSubscr != 0) nameChangeSubscr.cancel();
    }
    p.name = "name ${i++}";
  });
}