Question

嘿，我正在尝试测试以下示例装饰代码。它看起来很简单，但是当我运行它时，出现以下错误 “无法读取未定义的属性”名字”。似乎“ this”不能引用当前上下文。有想法吗？

class Customer { 
  @hashify 
  public firstname: string; 
  public lastname: string; 

  constructor(firstname : string, lastname : string) { 
    this.firstname = firstname; 
    this.lastname = lastname; 
  } 
}

function hashify(target: any, key: string) { 
  var _value = this[key]; 

  var getter = function () { 
        return '#' + _value; 
  }; 

  var setter = function (newValue) { 
    _value = newValue; 
  }; 

  if (delete this[key]) { 
    Object.defineProperty(target, key, { 
      get: getter, 
      set: setter, 
      enumerable: true, 
      configurable: true 
    }); 
  } 
}

Answer 1

您的代码唯一的问题是this值不正确。通过将该值更改为target，您的代码可以正常工作。

class Customer { 
  @hashify 
  public firstname: string; 
  public lastname: string; 

  constructor(firstname : string, lastname : string) { 
    this.firstname = firstname; 
    this.lastname = lastname; 
  } 
}

function hashify(target: any, key: string) { 
  var _value = target[key]; 

  var getter = function () { 
        return '#' + _value; 
  }; 

  var setter = function (newValue) { 
    _value = newValue; 
  }; 

  if (delete target[key]) { 
    Object.defineProperty(target, key, { 
      get: getter, 
      set: setter, 
      enumerable: true, 
      configurable: true 
    }); 
  } 
}

在您的示例中，这是因为target界面中的参数PropertyDecorator是对应用装饰器的对象的引用。

Angular 6属性装饰器问题

1 个答案: