Question

我一直在使用polymer.dart教程中的秒表示例。我已将@Observable String counter = '00:00';更改为：

String _counter = '00:00';
@published void set counter (String s){ _counter = s; }
@published String get counter => _counter;

我将它设置为@published所以我可以在html标记中设置counter属性，当我最初将其更改为@Published String counter = '00:00';但将其拆分为单独的getter和setter属性时，这非常有用根本不再有效，是否可以做这样的事情？我希望在以编程方式或通过用户/ html更改更改绑定值时执行一些自定义逻辑。

Answer 1

@observable仅在吸气剂上是必需的。

我想你想做的是

// additional functionality in the setter
String _counter = '00:00';
@PublishedProperty(reflect: true) 
String get counter => _counter;
void set counter (String s){ 
  _counter = s;  
  // do something ...
}

void attached() {
  new async.Timer.periodic(new Duration(seconds:1), (_) {
    var oldVal = _counter;
    var time = new DateTime.now();
    _counter = '${time.minute}:${time.second}';
    // explicitely notify Polymer about the changed value
    notifyPropertyChange(#counter, oldVal, _counter);
  });
}

或者

// additional functionality in xxxChanged
@PublishedProperty(reflect: true) 
String counter = '00:00';

void counterChanged(oldVal, newVal){ 
  // do something ...
}

另一个是

// use readValue/writeValue to fix some timing issues
@PublishedProperty(reflect: true) 
String get counter => readValue(#counter);
void set counter (String s){ 
  writeValue(#counter, s); 
  // do something ...
}

//in the constructor
writeValue(#counter, '00:00');

@PublishedProperty(reflect: true)确保使用字段值更新HTML属性。

如果你发现这令人困惑，你并不孤单......

是否可以在polymer.dart中发布匹配的getter和setter属性？

1 个答案: