Associated Library in QTP not working - functional-testing

Question

I am new to QTP, just started using it. I have written one class definition in some functional library and also created a test as under:
Class ExcelFileReader
Public default Function Init(pathToExcel)
Dim objFSO
Dim result
Set objFSO = CreateObject("Scripting.FileSystemObject")
If objFSO.FileExists(pathToExcel) Then
Rem File Found
Dim objExcel
Set objExcel = CreateObject("Excel.Application")
objExcel.Workbooks.open(pathToExcel)
Else
REM File not found
result = vbOk
While result <> vbCancel
result = Msgbox ("Unable to Locate the file", 5, "Error")
Wend
ExitAction(1)
End If
End Function
End Class
Test:
Dim objExcelReader : Set objExcelReader = New ExcelFileReader
objExcelReader.Init("D:\mytest.xlsx")
I have associated the functional library with the test but still I am getting an error at line number 2 in test stating class definition not found. Also if I copy complete code in the same file "test" then the things are working as intended.
Thanks in advance :)

Answer 1

Classes have local scope in your library. You have to construct them with a public function to make them publicly available:
Public Function new_ExcelFileReader()
Set new_ExcelFileReader = new ExcelFileReader
End Function
Class ExcelFileReader
Sub Class_Initialize
MsgBox "Present!"
End Sub
End Class
And in your other library:
Dim objExcelReader : Set objExcelReader = New_ExcelFileReader
objExcelReader.Init("D:\mytest.xlsx")
Protip: You can pass initialization parameters into your constructor function.
EDIT
On request: how to pass constructor parameters. Just add them to your constructor function:
Public Function new_ExcelFileReader2(filepath, sheetname)
Set new_ExcelFileReader2 = new ExcelFileReader
new_ExcelFileReader2.Init(filepath, sheetname)
End Function
' And the call:
Set myExcelFileReader = new_ExcelFileReader2("C:\temp\tempExcel.xlsx", "sheet1")
In my implementation I have sometimes the same object, but that gets 'configured' by multiple contructor functions. In your case you could have a new_ExcelFileReader, a new_CSVFileReader and a new_TabDelimitedReader all pointing to the same object but configured differently.
Another way to fancy up your code is to return the object (with the me keyword) by the init function. This will result in code like this:
Class ExcelFileReader
private filepath_
public function Init(filepath)
filepath_ = filepath
Set Init = me
end function
End Class
Set myExcelFileReader = new ExcelFileReader.Init("C:\temp\tmpExcel.xlsx")
With a constructor function you can use it by just returning the object and then calling the Init function.
Public Function new_ExcelFileReader() ' this is the same as the first function
Set new_ExcelFileReader = new ExcelFileReader
End Function
Set myExcelFileReader = new_ExcelFileReader.Init("C:\temp\tmpExcel.xlsx")