如何動態引用VBA中的對象屬性

Question

我正在嘗試編寫一個VBA函數，該函數可以根據對象的某個屬性的值來計算集合中的對象。我需要被檢查的對象屬性是動態的，由函數參數提供。我可以使用if then聲明，但是這將有許多很多elseif子句，每個子句都具有相同的過程，但屬性名稱除外。

我想避免重複我的代碼重複每個屬性的名稱。這是迄今爲止我所擁有的。

Private Function getTicketCount(c As Collection, f As String, s As String) _ 
As Long 
' @param c: collection of Ticket objects. 
' @param f: property to filter. 
' @param s: filter string. 
' 
' Function returns number of tickets that pass the filter. 

Dim x As Long 
Dim t As Ticket 

x = 0 

For Each t In c 
    If t.f = s Then x = x + 1 ' Compiler throws "Method or data member not found." 
Next t 

getTicketCount = x 
End Function 

我遇到的問題是編譯器正在尋找t的「f」屬性而不是t的f值屬性。確切的錯誤在上面的代碼塊中註釋。我如何使用f的值而不是「f」來引用對象屬性？

Answer 1

我相信你想使用CallByName方法CallByName MSDN Link

Private Function getTicketCount(c As Collection, f As String, s As String) _ 
As Long 
' @param c: collection of Ticket objects. 
' @param f: property to filter. 
' @param s: filter string. 
' 
' Function returns number of tickets that pass the filter. 

Dim x As Long 
Dim t As Ticket 

x = 0 

For Each t In c 
    If CallByName(t, f, VbGet) = s Then x = x + 1 ' Compiler throws "Method or data member not found." 
Next t 

getTicketCount = x 
End Function