Dart：使用带有多个getter / setter的observale [英] Dart: Using observale with multiple getters/setter

问题描述

对于我的Polymer应用程序我需要一个observable在两种不同的口味，例如作为一个整数值和字符串值。我使用getters和setters来封装状态和内部表示。通过这样做，我必须实现 notifyPropertyChange 每个观察者在每个setter，这导致了大量的errorphrone管道代码。例如
我需要两次 notifyPropertyChange - 两种口味的语句，如果我必须使用
4种口味，我必须使用4 * 4 = 16 notifyPropertyChange - 语句。我修改了点击计数器示例来说明这一点：

  @CustomTag（'click-counter'）
 class ClickCounter extends PolymerElement {
 int _count; 
 @observable int get count => _计数; 
 @observable set count（int val）{
 notifyPropertyChange（＃count，_count，val）; 
 _count = notifyPropertyChange（＃strcount，_count，val）;} 
 
 @observable String get strcount {
 print（TOSTRING+ _count.toString（））; 
 return _count.toString（）;} 
 
 @observable set strcount（String val）{
 notifyPropertyChange（＃strcount，_count，int.parse（val））; 
 _count = notifyPropertyChange（＃count，_count，int.parse（val））;} 
 
 ClickCounter.created（）：super.created（）{
} 
 
 void increment（）{
 count ++; 
} 
} 
  

有没有更好的方法来实现这么多 notifyPropertyChange - 语句？

尊敬

Markus

解决方案

我没有测试它，但它应该工作，我认为它显着更少的代码，如果你有更多的这样的属性。

类别ClickCounter extends PolymerElement {$（




















$ b b $ b int _count;
@observable int get count => _计数;
set count（int val）{
notifyPropertyChange（＃count，_count，val）;
notifyPropertyChange（#strcount，_count.toString（），val.toString（））;
_count = val;

@observable String get strcount {
// print（TOSTRING+ _count.toString（））;
return _count.toString（）;}

set strcount（String val）{
count = int.parse（val）; //设置新的值使用setter不是字段来触发属性更改
}

ClickCounter.created（）：super.created（）;

void increment（）{
count ++;
}
}

for my Polymer-application I need one observable in two different flavors, for example as an integer-value and and string-value. I use getters and setters to encapsulate the state and internal representation. By doing this I have to implement notifyPropertyChange for every observable in every setter, which leads to much errorphrone plumbing code. For example I need two times to notifyPropertyChange-Statements for two flavors, if I have to use 4 flavors, I have to use 4*4 = 16 notifyPropertyChange-Statements. I have modified the click-counter example to illustrate this:

@CustomTag('click-counter')
class ClickCounter extends PolymerElement {
  int _count;
  @observable int get count => _count;
  @observable set count(int val) {
    notifyPropertyChange(#count,_count,val);
    _count = notifyPropertyChange(#strcount,_count,val);}

  @observable String get strcount { 
    print("TOSTRING "+_count.toString()); 
    return _count.toString();}

  @observable set strcount(String val) { 
    notifyPropertyChange(#strcount,_count,int.parse(val));
    _count = notifyPropertyChange(#count,_count,int.parse(val));}

  ClickCounter.created() : super.created() {
  }

  void increment() {
    count++;
  }
}

Is there a better way to implement this without so much notifyPropertyChange-Statements?

Regards

Markus

解决方案

I have not tested it, but it should work and I think its notable less code if you have more such properties.

@CustomTag('click-counter')
class ClickCounter extends PolymerElement {
  int _count;
  @observable int get count => _count;
  set count(int val) { 
    notifyPropertyChange(#count,_count,val);
    notifyPropertyChange(#strcount, _count.toString(), val.toString());
    _count = val;

  @observable String get strcount { 
    // print("TOSTRING "+_count.toString()); 
    return _count.toString();}

  set strcount(String val) { 
    count = int.parse(val); // set the new value using the setter not the field to fire property change
  }

  ClickCounter.created() : super.created();

  void increment() {
    count++;
  }
}

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