Load custom-compiled SQLite DLLs from a user folder using a class module
This example comes from a separate project, the SQLiteCAdo VBA library, which uses DllManager for loading the SQLite DLL with dependencies. Below is a stripped-down version of the SQLiteC class, responsible for the setup/teardown processes (DllManagerDemoSQLiteC class in the DllTools.Manager.Demo RD Code Explorer folder). The setup is similar to the previous example, except that the calling code instantiates the DllManagerDemoSQLiteC class, which, in turn, instantiates DllManager.
DllManagerDemoSQLiteC has the predeclared attribute set and employs the Factory/Constructor (Create/Init) pattern. For illustrative purposes, only one SQLite function declaration remains in the class. Private structure TObjectState encapsulates private instance fields (variable this), including a reference to a DllManager instance.
DllManagerDemoSQLiteC.cls
'@PredeclaredId
Option Explicit
#If VBA7 Then
Private Declare PtrSafe Function sqlite3_libversion_number Lib "SQLite3" () As Long
#Else
Private Declare Function sqlite3_libversion_number Lib "SQLite3" () As Long
#End If
Private Type TObjectState
DllMan As DllManager
Connections As Scripting.Dictionary
End Type
Private this As TObjectState
Public Function Create(ByVal DllPath As String, _
Optional ByVal DllNames As Variant = Empty) As DllManagerDemoSQLiteC
Dim Instance As DllManagerDemoSQLiteC
Set Instance = New DllManagerDemoSQLiteC
Instance.Init DllPath, DllNames
Set Create = Instance
End Function
Friend Sub Init(ByVal DllPath As String, _
Optional ByVal DllNames As Variant = Empty)
Dim FileNames As Variant
If Not IsEmpty(DllNames) Then
FileNames = DllNames
Else
#If Win64 Then
FileNames = "sqlite3.dll"
#Else
FileNames = Array("icudt68.dll", "icuuc68.dll", "icuin68.dll", _
"icuio68.dll", "icutu68.dll", "sqlite3.dll")
#End If
End If
Set this.DllMan = DllManager.Create(DllPath, FileNames)
Set this.Connections = New Scripting.Dictionary
this.Connections.CompareMode = TextCompare
End Sub
Public Function Version() As Long
Version = sqlite3_libversion_number()
End Function
The RubberDuck Addin, if available, can activate the predeclared class attribute. Otherwise, an auto-assigned module- or project-level variable named after the class can act as a predeclared instance:
Private/Public DllManagerDemoSQLiteC as New DllManagerDemoSQLiteC
In the former case, this command executed from the immediate pane prints the SQLite version number:
?DllManagerDemoSQLiteC.Create("").Version
This class can be instantiated from a standard module, for example:
Private Sub InitDBQC()
Dim DllPath As String
Dim DllNames As Variant
#If Win64 Then
DllPath = ThisWorkbook.Path & "\Library\DllTools\dll\x64"
DllNames = "sqlite3.dll"
#Else
DllPath = ThisWorkbook.Path & "\Library\DllTools\dll\x32"
DllNames = Array("icudt68.dll", "icuuc68.dll", "icuin68.dll", _
"icuio68.dll", "icutu68.dll", "sqlite3.dll")
#End If
Dim dbm As DllManagerDemoSQLiteC
Set dbm = DllManagerDemoSQLiteC.Create(DllPath, DllNames)
If dbm Is Nothing Then
Err.Raise ErrNo.ObjectCreateErr, "SQLiteCExamples", _
"Failed to create an DllManagerDemoSQLiteC instance."
Else
Debug.Print "Database manager instance (DllManagerDemoSQLiteC class) is ready"
Debug.Print "SQLite version number: " & CStr(dbm.Version())
End If
DllManagerDemo from the same Code Explorer folder (DllTools.Manager.Demo) demonstrates a similar functionality executed from a standard module directly.