IsObject Function

Returns a Boolean value indicating whether an identifier represents an object variable.

Syntax

IsObject(identifier)

Parameters

identifier (Required): Variable name to test

Return Value

Returns a Boolean: - True if the identifier is an object variable (Object, Form, Control, etc.) - False if the identifier is not an object variable - Returns True for any object reference (including Nothing) - Returns False for numeric types, strings, dates, arrays of non-objects - Returns False for Null and Empty - Works with Variant variables containing object references - Use to determine if variable can be used with Set statement

Remarks

The IsObject function is used to determine whether a variable is an object reference: - Returns True for any object variable type (Form, Control, Collection, etc.) - Returns True even if object is Nothing (uninitialized object reference) - Returns False for value types (Integer, String, Double, Boolean, etc.) - Returns False for Null and Empty - Useful before calling object methods or properties - Use to determine if Set statement is needed for assignment - Common in COM/ActiveX programming - Works with Variant variables containing object references - Cannot distinguish between different object types (use TypeOf...Is for that) - VarType(var) = vbObject provides similar but not identical information - Important for proper cleanup (setting objects to Nothing) - Use before accessing object members to avoid errors

Typical Uses

Object Detection: Check if variable contains an object reference
Assignment Logic: Determine whether to use Set or regular assignment
Cleanup Verification: Verify objects are properly set to Nothing
Error Prevention: Avoid "Object required" errors
Type Validation: Validate function parameters are objects
COM Interop: Work with late-bound COM objects
Collection Processing: Handle mixed collections of objects and values
Variant Handling: Determine if Variant contains object or value

Basic Usage Examples

' Example 1: Basic object detection
Dim obj As Object
Dim str As String
Dim num As Integer
Set obj = CreateObject("Scripting.Dictionary")
str = "Hello"
num = 123
Debug.Print IsObject(obj)      ' True - object variable
Debug.Print IsObject(str)      ' False - string variable
Debug.Print IsObject(num)      ' False - numeric variable
' Example 2: Nothing is still an object type
Dim myObj As Object
Set myObj = Nothing
Debug.Print IsObject(myObj)    ' True - object type (even though Nothing)
' Example 3: Various object types
Dim frm As Form
Dim col As Collection
Dim dict As Object
Set frm = New Form1
Set col = New Collection
Set dict = CreateObject("Scripting.Dictionary")
Debug.Print IsObject(frm)      ' True - Form object
Debug.Print IsObject(col)      ' True - Collection object
Debug.Print IsObject(dict)     ' True - Dictionary object
' Example 4: Determine assignment method
Sub AssignValue(target As Variant, source As Variant)
    If IsObject(source) Then
        Set target = source    ' Use Set for objects
    Else
        target = source        ' Regular assignment for values
    End If
End Sub

Common Patterns

' Pattern 1: Safe object cleanup
Sub CleanupObject(ByRef obj As Variant)
    If IsObject(obj) Then
        Set obj = Nothing
    End If
End Sub
' Pattern 2: Check if object is set before use
Function SafeCallMethod(obj As Variant) As Boolean
    If IsObject(obj) Then
        If Not obj Is Nothing Then
            obj.SomeMethod
            SafeCallMethod = True
        Else
            SafeCallMethod = False
        End If
    Else
        SafeCallMethod = False
    End If
End Function
' Pattern 3: Copy with correct assignment
Function CopyValue(source As Variant) As Variant
    If IsObject(source) Then
        Set CopyValue = source
    Else
        CopyValue = source
    End If
End Function
' Pattern 4: Count objects in collection
Function CountObjects(items As Collection) As Long
    Dim count As Long
    Dim item As Variant
    count = 0
    For Each item In items
        If IsObject(item) Then
            count = count + 1
        End If
    Next item
    CountObjects = count
End Function
' Pattern 5: Validate function parameter
Function ProcessObject(obj As Variant) As Boolean
    If Not IsObject(obj) Then
        Err.Raise 5, , "Object parameter required"
    End If
    If obj Is Nothing Then
        Err.Raise 91, , "Object not set"
    End If
    ' Process object
    ProcessObject = True
End Function
' Pattern 6: Generic value display
Function ValueToString(value As Variant) As String
    If IsNull(value) Then
        ValueToString = "Null"
    ElseIf IsEmpty(value) Then
        ValueToString = "Empty"
    ElseIf IsObject(value) Then
        If value Is Nothing Then
            ValueToString = "Nothing"
        Else
            ValueToString = TypeName(value) & " object"
        End If
    Else
        ValueToString = CStr(value)
    End If
End Function
' Pattern 7: Clone array with proper assignment
Function CloneArray(arr As Variant) As Variant
    Dim result() As Variant
    Dim i As Long
    If Not IsArray(arr) Then
        CloneArray = arr
        Exit Function
    End If
    ReDim result(LBound(arr) To UBound(arr))
    For i = LBound(arr) To UBound(arr)
        If IsObject(arr(i)) Then
            Set result(i) = arr(i)
        Else
            result(i) = arr(i)
        End If
    Next i
    CloneArray = result
End Function
' Pattern 8: Release all objects in array
Sub ReleaseObjects(arr As Variant)
    Dim i As Long
    If Not IsArray(arr) Then Exit Sub
    For i = LBound(arr) To UBound(arr)
        If IsObject(arr(i)) Then
            Set arr(i) = Nothing
        End If
    Next i
End Sub
' Pattern 9: Filter objects from collection
Function GetObjects(items As Collection) As Collection
    Dim result As New Collection
    Dim item As Variant
    For Each item In items
        If IsObject(item) Then
            result.Add item
        End If
    Next item
    Set GetObjects = result
End Function
' Pattern 10: Compare values with object handling
Function AreEqual(val1 As Variant, val2 As Variant) As Boolean
    If IsObject(val1) And IsObject(val2) Then
        AreEqual = (val1 Is val2)  ' Use Is for object comparison
    ElseIf IsObject(val1) Or IsObject(val2) Then
        AreEqual = False  ' One object, one value - not equal
    Else
        AreEqual = (val1 = val2)  ' Regular comparison for values
    End If
End Function

Advanced Usage Examples

' Example 1: Generic collection wrapper
Public Class GenericCollection
    Private m_items As Collection
    Private Sub Class_Initialize()
        Set m_items = New Collection
    End Sub
    Public Sub Add(item As Variant)
        If IsObject(item) Then
            m_items.Add item
        Else
            m_items.Add item
        End If
    End Sub
    Public Function Item(index As Variant) As Variant
        If IsObject(m_items(index)) Then
            Set Item = m_items(index)
        Else
            Item = m_items(index)
        End If
    End Function
    Public Sub Clear()
        Dim i As Long
        For i = m_items.Count To 1 Step -1
            If IsObject(m_items(i)) Then
                Set m_items(i) = Nothing
            End If
        Next i
        Set m_items = New Collection
    End Sub
    Public Function Count() As Long
        Count = m_items.Count
    End Function
End Class
' Example 2: Object lifecycle manager
Public Class ObjectManager
    Private m_objects As Collection
    Private Sub Class_Initialize()
        Set m_objects = New Collection
    End Sub
    Public Sub Register(obj As Variant, Optional key As String = "")
        If Not IsObject(obj) Then
            Err.Raise 5, , "Only objects can be registered"
        End If
        If key = "" Then
            m_objects.Add obj
        Else
            m_objects.Add obj, key
        End If
    End Sub
    Public Sub UnregisterAll()
        Dim i As Long
        For i = m_objects.Count To 1 Step -1
            If IsObject(m_objects(i)) Then
                Set m_objects(i) = Nothing
            End If
        Next i
        Set m_objects = New Collection
    End Sub
    Public Function GetStats() As String
        Dim msg As String
        Dim i As Long
        Dim objectCount As Long
        Dim nothingCount As Long
        objectCount = 0
        nothingCount = 0
        For i = 1 To m_objects.Count
            If IsObject(m_objects(i)) Then
                If m_objects(i) Is Nothing Then
                    nothingCount = nothingCount + 1
                Else
                    objectCount = objectCount + 1
                End If
            End If
        Next i
        msg = "Total: " & m_objects.Count & vbCrLf
        msg = msg & "Active Objects: " & objectCount & vbCrLf
        msg = msg & "Nothing: " & nothingCount
        GetStats = msg
    End Function
    Private Sub Class_Terminate()
        UnregisterAll
    End Sub
End Class
' Example 3: Variant inspector utility
Public Class VariantInspector
    Public Function Inspect(value As Variant) As String
        Dim info As String
        info = "VarType: " & VarType(value) & vbCrLf
        info = info & "TypeName: " & TypeName(value) & vbCrLf
        If IsNull(value) Then
            info = info & "State: Null" & vbCrLf
        ElseIf IsEmpty(value) Then
            info = info & "State: Empty" & vbCrLf
        ElseIf IsObject(value) Then
            info = info & "State: Object" & vbCrLf
            If value Is Nothing Then
                info = info & "Value: Nothing" & vbCrLf
            Else
                info = info & "Value: [" & TypeName(value) & " instance]" & vbCrLf
            End If
        ElseIf IsArray(value) Then
            info = info & "State: Array" & vbCrLf
            info = info & "Bounds: " & LBound(value) & " to " & UBound(value) & vbCrLf
        Else
            info = info & "State: Value" & vbCrLf
            info = info & "Value: " & value & vbCrLf
        End If
        Inspect = info
    End Function
End Class
' Example 4: Smart assignment utility
Public Class SmartAssignment
    Public Sub Assign(ByRef target As Variant, source As Variant)
        On Error GoTo ErrorHandler
        If IsObject(source) Then
            Set target = source
        Else
            target = source
        End If
        Exit Sub
    ErrorHandler:
        Err.Raise Err.Number, "SmartAssignment", _
                  "Failed to assign: " & Err.Description
    End Sub
    Public Sub CopyArray(ByRef target As Variant, source As Variant)
        Dim i As Long
        If Not IsArray(source) Then
            Err.Raise 5, , "Source must be an array"
        End If
        ReDim target(LBound(source) To UBound(source))
        For i = LBound(source) To UBound(source)
            If IsObject(source(i)) Then
                Set target(i) = source(i)
            Else
                target(i) = source(i)
            End If
        Next i
    End Sub
    Public Sub ReleaseArray(ByRef arr As Variant)
        Dim i As Long
        If Not IsArray(arr) Then Exit Sub
        For i = LBound(arr) To UBound(arr)
            If IsObject(arr(i)) Then
                Set arr(i) = Nothing
            Else
                arr(i) = Empty
            End If
        Next i
        Erase arr
    End Sub
End Class

Error Handling

The IsObject function itself does not raise errors:

' IsObject is safe to call on any variable
Dim obj As Object
Dim str As String
Dim num As Integer
Debug.Print IsObject(obj)      ' True - even if Nothing
Debug.Print IsObject(str)      ' False
Debug.Print IsObject(num)      ' False
' Common pattern: check before object operations
Sub ProcessParameter(param As Variant)
    If Not IsObject(param) Then
        Err.Raise 5, , "Object required"
    End If
    If param Is Nothing Then
        Err.Raise 91, , "Object not set"
    End If
    ' Safe to use param as object
    param.DoSomething
End Sub

Performance Considerations

Fast Operation: IsObject is a very fast type check
Variant Overhead: Using Variant variables has more overhead than typed variables
Early Binding: When possible, use typed object variables for better performance
Frequent Checks: Cache results if checking same variable multiple times

Best Practices

Check Before Use: Use IsObject before accessing object members
Proper Assignment: Use Set for object assignment, regular = for values
Cleanup Objects: Set object variables to Nothing when done
Combine with Is Nothing: Check both IsObject and Is Nothing for complete validation
Type-Specific Checks: Use TypeOf...Is for specific object type testing
Error Handling: Provide clear error messages for type mismatches
Variant Collections: Use IsObject when working with mixed-type collections
Documentation: Clearly document when functions accept/return objects

Function	Purpose	Returns	Use Case
`IsObject`	Check if object type	`Boolean`	Detect object variables
`TypeOf...Is`	Check specific object type	`Boolean`	Test for specific class/interface
`Is Nothing`	Check if object is Nothing	`Boolean`	Test if object is initialized
`VarType`	Get variant type	`Integer`	Detailed type information
`TypeName`	Get type name	`String`	Type name as string
`IsNull`	Check if `Null`	`Boolean`	Detect `Null` values
`IsEmpty`	Check if uninitialized	`Boolean`	Detect Empty Variants

`IsObject` vs `TypeOf...Is`

Dim obj As Object
Dim frm As Form
Set obj = New Collection
Set frm = New Form1
' IsObject checks if variable is any object type
Debug.Print IsObject(obj)           ' True
Debug.Print IsObject(frm)           ' True
' TypeOf...Is checks for specific object type
Debug.Print TypeOf obj Is Collection    ' True
Debug.Print TypeOf obj Is Form          ' False
Debug.Print TypeOf frm Is Form          ' True
Debug.Print TypeOf frm Is Collection    ' False
' Use IsObject for general object detection
' Use TypeOf...Is for specific type validation

`IsObject` with `Nothing`

Dim obj As Object
' Object variable not set
Debug.Print IsObject(obj)       ' True - it's an object type
Debug.Print obj Is Nothing      ' True - but not initialized
' Set to Nothing explicitly
Set obj = Nothing
Debug.Print IsObject(obj)       ' True - still object type
Debug.Print obj Is Nothing      ' True
' Proper validation pattern
If IsObject(obj) Then
    If Not obj Is Nothing Then
        ' Safe to use obj
        obj.DoSomething
    Else
        ' Object type but not initialized
        MsgBox "Object not set"
    End If
Else
    ' Not an object type
    MsgBox "Not an object"
End If

Platform and Version Notes

Available in all VB6 versions
Part of VBA core functions
Returns Boolean type
Works with all object types (Form, Control, Collection, COM objects, etc.)
Returns True for Nothing (object type, but not initialized)
Critical for proper object lifecycle management

Limitations

Cannot distinguish between different object types (use TypeOf...Is)
Returns True for Nothing (need to check Is Nothing separately)
Cannot detect if object has been destroyed/released externally
Does not validate object's internal state or usability
Cannot determine object's capabilities or supported interfaces

TypeOf...Is: Check if object is specific type
Is Nothing: Check if object reference is Nothing
VarType: Get detailed Variant type information (vbObject = 9)
TypeName: Get type name as string
IsNull: Check if Variant is Null
IsEmpty: Check if Variant is Empty