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基本クラスBaseParserから継承する2つのParserクラスがあります。どちらかのクラスを別のMonitorクラスのパラメーターとして使用したいと思います。パーサークラスCS600とTCH600には、RawDataListとSummaryDataListの2つのプロパティがあります。CS600クラスのRawDataListは、（CS600Dataの）リストを返します。TCH600 RawDataListは、（TCH600Dataの）リストを返します。SummaryDataListは、各パーサークラスで同様のクラスを返します。CS600DataおよびTCH600Dataは、基本クラスBaseDataから派生します。BaseParserには、RawDataList（List（of BaseData））およびSummaryDataList（List（of BaseSummaryData））もあります。

Monitorクラスには、上記の2つの具象パーサーのいずれかになり得るプライベートフィールド_thisParserがあります。Monitorクラス内で_thisParserのRawDataListとSummaryDataListを呼び出して使用できるようにしたいのですが、具体的なParserクラスを作成すると、Visual Studioは、CS600のRawDataListプロパティは、戻り値が異なるため、BaseParserのRawDataListプロパティをオーバーライドできないことに注意します。タイプ。

CS600DataはBaseDataから派生しているので（ただし、独自の新しいプロパティもいくつか追加されているため）、BaseDataを使用する場所ならどこでもCS600Dataを使用できると思いました。私は何を誤解していますか？これらのクラスを正しく構築するにはどうすればよいですか？

Public MustInherit Class BaseParser

    Protected _rawDataList As List(Of RawGasData.BaseData)
    Public MustOverride ReadOnly Property RawDataList() As List(Of RawGasData.BaseData)

    Protected _summaryDataList As List(Of SummaryGasData.BaseSummaryData)
    Public MustOverride ReadOnly Property SummaryDataList() As List(Of SummaryGasData.BaseSummaryData)

    Public Event GasDataCreated(ByVal sender As Object, ByVal e As EventArgs)

    Public Sub New()
    End Sub

    Public Sub New(ByVal dataFilePath As String, ByVal unit As String)
        Load(dataFilePath, unit)
    End Sub

    Public Sub Load(ByVal dataFilePath As String, ByVal unit As String)
        Dim contents = My.Computer.FileSystem.ReadAllText(dataFilePath)
        ParseRawData(contents)
        GenerateSummaryData(contents, unit)
        RaiseEvent GasDataCreated(Me, EventArgs.Empty)
    End Sub

    Protected MustOverride Sub ParseRawData(ByVal fileContents As String)

    Protected MustOverride Sub GenerateSummaryData(ByVal fileContents As String, ByVal unit As String)

End Class

Public Class CS600Parser
    Inherits BaseParser

    Shadows _rawDataList As List(Of RawGasData.CS600Data)
    'Cannot override base class' RawDataList - differ by their return types
    Public Overrides ReadOnly Property RawDataList() As List(Of RawGasData.CS600Data)
        Get
            Return _rawDataList
        End Get
    End Property

    Shadows _summaryDataList As List(Of SummaryGasData.CS600SummaryData)
    'Cannot override base class' SummaryDataList - differ by their return types
    Public Overrides ReadOnly Property SummaryDataList() As List(Of SummaryGasData.CS600SummaryData)
        Get
            Return _summaryDataList
        End Get
    End Property

    Protected Overrides Sub ParseRawData(ByVal fileContents As String)
        Dim data = From d In fileContents.Trim.Split(CChar(vbCrLf)) _
                   Let fields = d.Split(","c).Select(Function(s) s.Trim) _
                   Select New RawGasData.CS600Data With { _
                        .SampleNumber = fields(0), _
                        .UserID = fields(1), _
                        .CarbonValue = CDbl(fields(2)), _
                        .SulfurValue = CDbl(fields(3))}

        _rawDataList = data.ToList

    End Sub

    Protected Overrides Sub GenerateSummaryData(ByVal fileContents As String, ByVal unit As String)
        Dim groupedData = From d In _rawDataList _
                          Group By d.SampleNumber Into Group _
                          Select New SummaryGasData.CS600SummaryData With { _
                            .DataTimeStamp = Now, _
                            .SampleNumber = SampleNumber, _
                            .UserID = Group.First.UserID, _
                            .CarbonAverage = Group.Select(Function(s) s.CarbonValue).Average, _
                            .CarbonUnit = unit, _
                            .SulfurAverage = Group.Select(Function(s) s.SulfurValue).Average, _
                            .SulfurUnit = unit}

        _summaryDataList = groupedData.ToList

    End Sub

End Class

Public Class TCHParser
    Inherits BaseParser

    Shadows _rawDataList As List(Of RawGasData.TCH600Data)
    'Cannot override base class' RawDataList - differ by their return types
    Public Overrides ReadOnly Property RawDataList() As List(Of RawGasData.TCH600Data)
        Get
            Return _rawDataList
        End Get
    End Property

    Shadows _summaryDataList As List(Of SummaryGasData.TCH600SummaryData)
    'Cannot override base class' SummaryDataList - differ by their return types
    Public Overrides ReadOnly Property SummaryDataList() As List(Of SummaryGasData.TCH600SummaryData)
        Get
            Return _summaryDataList
        End Get
    End Property

    Protected Overrides Sub ParseRawData(ByVal fileContents As String)
        Dim data = From d In fileContents.Trim.Split(CChar(vbCrLf)) _
       Let fields = d.Split(","c).Select(Function(s) s.Trim) _
       Select New RawGasData.TCH600Data With { _
            .SampleNumber = fields(0), _
            .UserID = fields(1), _
            .OxygenValue = CDbl(fields(2)), _
            .NitrogenValue = CDbl(fields(3)), _
            .HydrogenValue = CDbl(fields(4)), _
            .MassUsed = CDbl(fields(5))}

        _rawDataList = data.ToList

    End Sub

    Protected Overrides Sub GenerateSummaryData(ByVal fileContents As String, ByVal unit As String)
        Dim groupedData = From d In _rawDataList _
                          Group By d.SampleNumber Into Group _
                          Select New SummaryGasData.TCH600SummaryData With { _
                            .DataTimeStamp = Now, _
                            .SampleNumber = SampleNumber, _
                            .UserID = Group.First.UserID, _
                            .OxygenAverage = Group.Select(Function(s) s.OxygenValue).Average, _
                            .OxygenUnit = unit, _
                            .NitrogenAverage = Group.Select(Function(s) s.NitrogenValue).Average, _
                            .NitrogenUnit = unit, _
                            .HydrogenAverage = Group.Select(Function(s) s.HydrogenValue).Average, _
                            .HydrogenUnit = unit}

        _summaryDataList = groupedData.ToList
    End Sub


End Class


 Public MustInherit Class BaseData
    Implements IGasData

    Private _massUsed As Double
    Public Property MassUsed() As Double Implements IGasData.MassUsed
        Get
            Return _massUsed
        End Get
        Set(ByVal value As Double)
            _massUsed = value
        End Set
    End Property

    Private _sampleNumber As String
    Public Property SampleNumber() As String Implements IGasData.SampleNumber
        Get
            Return _sampleNumber
        End Get
        Set(ByVal value As String)
            _sampleNumber = value
        End Set
    End Property

    Private _userID As String
    Public Property UserID() As String Implements IGasData.UserID
        Get
            Return _userID
        End Get
        Set(ByVal value As String)
            _userID = value
        End Set
    End Property
End Class

Public Class CS600Data
    Inherits BaseData


    Private _carbonValue As Double
    Public Property CarbonValue() As Double
        Get
            Return _carbonValue
        End Get
        Set(ByVal value As Double)
            _carbonValue = value
        End Set
    End Property


    Private _sulfurValue As Double
    Public Property SulfurValue() As Double
        Get
            Return _sulfurValue
        End Get
        Set(ByVal value As Double)
            _sulfurValue = value
        End Set
    End Property

End Class

Public Class TCH600Data
    Inherits BaseData

    Private _oxygenValue As Double
    Public Property OxygenValue() As Double
        Get
            Return _oxygenValue
        End Get
        Set(ByVal value As Double)
            _oxygenValue = value
        End Set
    End Property


    Private _nitrogenValue As Double
    Public Property NitrogenValue() As Double
        Get
            Return _nitrogenValue
        End Get
        Set(ByVal value As Double)
            _nitrogenValue = value
        End Set
    End Property


    Private _hydrogenValue As Double
    Public Property HydrogenValue() As Double
        Get
            Return _hydrogenValue
        End Get
        Set(ByVal value As Double)
            _hydrogenValue = value
        End Set
    End Property

End Class
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1 に答える 1

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などのオーバーライドされたリストプロパティは、ポリモーフィズムが機能するための派生クラスではなく、RawDataList抽象基本クラスのタイプ（またはさらに良い）である必要があります。IGasDataタイプのリストを作成するBaseDataかIGasData、問題を引き起こしていることがわかった場合は、設計がリスコフの置換原則に準拠しているかどうかを確認することをお勧めします。

コンパイルして正常に実行される簡略化された図（VB.Net 2010）：

Sub Main    
    Dim parser As BaseParser = New TCHParser()
    Console.WriteLine(parser)   
End Sub

Public MustInherit Class BaseData    
    Public Property SampleNumber() As String
End Class

Public Class TCH600Data 
    Inherits BaseData

    Public Property OxygenValue() As Double
End Class

Public MustInherit Class BaseParser
    Public MustOverride ReadOnly Property RawDataList As List(of BaseData)
End Class

TCHParserプロパティを上書きしても問題なく動作しRawDataListます。Protected _rawDataListまた、抽象基本クラスにフィールドがあった理由もわかりません。それを削除すると、派生型でそのフィールドをシャドウイングすることを心配する必要がなくなります。

Public Class TCHParser 
    Inherits BaseParser

    ' Populate the list just so we can test easily.
    Public Sub New()
        Dim data As New List(Of BaseData)
        data.Add(New TCH600Data With {
            .SampleNumber = "1", _
            .OxygenValue = 1.5d })

        data.Add(New TCH600Data With {
            .SampleNumber = "2", _
            .OxygenValue = 2.5d })

        _rawDataList = data
    End Sub

    Private _rawDataList As List(of BaseData)  
    Public Overrides ReadOnly Property RawDataList As List(of BaseData)
        Get
            Return _rawDataList
        End Get
    End Property
End Class
于 2012-04-10T02:10:05.317 に答える