Question

我正在为我的大学任务做一个简单的ID生成器。但是现在我面临这个问题，它显示＆＃34;函数不会在所有路径上返回值＆＃34;。我得到的结果总是＆＃34; F＆＃34;路径。我该怎么办？

Private Function GenerateID(ByVal gender As String) As String

    Dim yearJoin As Int32 = Now.Year.ToString().Substring(2, 2)

    If String.Compare(gender, "Male") Then
        Return (yearJoin & "M" & (maxRows + 1).ToString("D3"))
    ElseIf String.Compare(gender, "Female") Then
        Return (yearJoin & "F" & (maxRows + 1).ToString("D3"))
    End If

End Function

Answer 1

如果匹配任何条件，只需返回一些默认值，如null：

Private Function GenerateID(ByVal gender As String) As String

    Dim yearJoin As Int32 = Now.Year.ToString().Substring(2, 2)

    If String.Compare(gender, "Male") Then
        Return (yearJoin & "M" & (maxRows + 1).ToString("D3"))
    ElseIf String.Compare(gender, "Female") Then
        Return (yearJoin & "F" & (maxRows + 1).ToString("D3"))
    End If
    Return Nothing
End Function

Answer 2

方法必须在任何情况下都返回一个值。因此，要么... Else添加If..ElseIf...，要添加最终Return something（作为后备值），要么在提供的gender不是{{1}的情况下抛出异常也不是Male。

我更喜欢后者（因为还有什么呢？）：

Female

您还应该使用Private Function GenerateID(ByVal gender As String) As String Dim yearJoin As String = Date.Today.Year.ToString().Substring(2, 2) Dim isMale As Boolean = String.Equals(gender, "Male", StringComparison.InvariantCultureIgnoreCase) Dim isFemale As Boolean = String.Equals(gender, "Female", StringComparison.InvariantCultureIgnoreCase) If Not isMale AndAlso Not isFemale Then Throw New ArgumentException($"{NameOf(gender)} must either be Male or Female", NameOf(gender)) End If Dim maleFemaleLetter = If(isMale, "M", "F") maxRows += 1 Dim id As String = $"{yearJoin}{maleFemaleLetter}{(maxRows).ToString("D3")}" Return id End Function。 Option Strict On返回一个整数。 String.Compare将此静默转换为Option Strict Off。请改用Boolean。与String.Equals相同，返回String.Substring而不是String。编写类型安全的代码以防止令人讨厌的错误。

如何解决这个问题＆＃34;函数不会在所有代码路径上返回值＆＃34;

2 个答案: