Question

我正在尝试实践观察者模式，如提供的代码所示。

主题，观察者和 DisplayElement 是接口类。 CurrentConditionsDisplay 类实现了 Observer 和 DisplayElement ，因此可以从 WeatherData 类进行更新。由于VBA不支持带参数的构造函数，因此我创建了一个子程序来保存weatherData对象，并使用它来注册 CURRENT OBJECT 。我使用 Me 传递当前对象。

当我运行主代码（ WeatherStation ）时，当我通过 Me 作为参数（ weatherData.registerObserver（Me））时，就会出现运行时错误438 ）。

非常感谢您的帮助。

观察者界面：

Option Compare Database
Option Explicit

Public Sub update(temperature As Double, humidity As Double, pressure As Double)
End Sub

主题界面：

Option Compare Database
Option Explicit

Public Sub registerObserver(o As Observer)
End Sub

Public Sub removeObserver(o As Observer)
End Sub

Public Sub notifyObservers()
End Sub

DisplayElement界面：

Option Compare Database
Option Explicit

Public Sub display()
End Sub

WeatherData子类：

Option Compare Database
Option Explicit

Implements Subject

Private m_observers As New Scripting.Dictionary
Private m_temperature As Double
Private m_humidity As Double
Private m_pressure As Double

Public Sub Subject_registerObserver(o As Observer)
    m_observers.Add o, o
End Sub

Public Sub Subject_removeObserver(o As Observer)
    If (m_observers.Exists(o)) Then
        m_observers.Remove (o)
    End If
End Sub

Public Sub Subject_notifyObservers()
    Dim i As Long
    Dim objeto As Observer

    For i = 0 To m_observers.Count - 1
        Set objeto = m_observers.Items(i)
        objeto.update m_temperature, m_humidity, m_pressure
    Next i
End Sub

Public Sub measurementsChanged()
    Call Subject_notifyObservers
End Sub

Public Sub setMeasurements(temperature As Double, humidity As Double, pressure As Double)
    m_temperature = temperature
    m_humidity = humidity
    m_pressure = pressure
    Call measurementsChanged
End Sub

CurrentConditionsDisplay子类：

Option Compare Database
Option Explicit

Implements Observer
Implements DisplayElement

Private m_temperature As Double
Private m_humidity As Double
Private m_weatherData As Subject

Public Sub CurrentConditionsDisplay(weatherData As Subject)
    Set m_weatherData = weatherData
    weatherData.registerObserver (Me)
End Sub

Public Sub Observer_update(temperature As Double, humidity As Double, pressure As Double)
    m_temperature = temperature
    m_humidity = humidity
    Call DisplayElement_display
End Sub

Public Sub DisplayElement_display()
    Debug.Print ("Current conditions: " + m_temperature + "F degrees and " + m_humidity + "% humidity")
End Sub

WeatherStation主要代码：

Option Compare Database
Option Explicit

Public Function WeatherStation()
    Dim wData As New weatherData
    Dim currentDisplay As New CurrentConditionsDisplay

    Call currentDisplay.CurrentConditionsDisplay(wData)
    Call wData.setMeasurements(80, 65, 30.4)
End Function

如何在Access / VBA

0 个答案: