`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

IsObject Function