7 Common Causes Of Run Time Error 91 And How To Fix Them

Run-time Error 91 can be one of the most frustrating issues that users encounter while working with Microsoft Excel or VBA (Visual Basic for Applications). If you've stumbled upon this error, you're not alone. This article will walk you through the common causes of Run-time Error 91 and how to resolve them effectively. Let’s dive in!

Understanding Run-time Error 91

Run-time Error 91 occurs when your code attempts to use an object that has not been set to an instance of an object. In simpler terms, this means that your program is trying to refer to something that doesn’t exist or hasn’t been properly initialized.

Common Causes of Run-time Error 91

1. Uninitialized Object Variables

   • One of the most frequent causes is when you attempt to access a method or property of an object variable that hasn’t been assigned a reference.

2. Using Nothing as an Object

   • If you declare an object but later set it to Nothing, and then try to use it, you will encounter this error.

3. Failed Object Creation

   • When creating an object, if the object creation fails, the variable remains uninitialized, and using it leads to Error 91.

4. Incorrect Object References

   • Attempting to reference an object that doesn’t exist (for example, a worksheet that has been deleted) will result in this error.

5. Late Binding Issues

   • If you are using late binding and the object type is not correctly specified, it can lead to this error, as the code won’t be able to recognize the object.

6. Object Lifecycle Issues

   • If the object is released before you try to use it, for instance, if it goes out of scope, it will result in a run-time error.

7. Explicit Declaration without Initialization

   • Declaring an object without actually initializing it can lead to trying to use a reference that does not point anywhere.

Fixing Run-time Error 91

Now that we’ve established the common causes, let's explore solutions to fix Error 91 effectively.

1. Initialize Your Object Variables Properly

Make sure to assign your object variables correctly before using them. For example:

Dim mySheet As Worksheet
Set mySheet = ThisWorkbook.Sheets("Sheet1")

2. Check for Nothing

Before accessing properties or methods of an object, check if it's set to Nothing. You can do this as follows:

If myObject Is Nothing Then
    ' Handle the error, or set it up
End If

3. Error Handling

Implement error handling to gracefully manage situations when an object cannot be created.

On Error Resume Next
Set myObject = CreateObject("Some.Object")
If Err.Number <> 0 Then
    MsgBox "Object creation failed."
    Err.Clear
End If

4. Validate Object References

Ensure that all your object references are valid before using them. This includes checking that sheets, ranges, or other objects exist.

5. Use Early Binding

If possible, use early binding instead of late binding to have better control and compile-time checking of objects. This can help in avoiding potential run-time errors.

6. Scope Management

Make sure your objects are in scope when you are trying to access them. Avoid releasing them prematurely.

7. Declaration with Initialization

Always declare and initialize your objects in one line when possible.

Dim myObject As New SomeObject

Table of Quick Fixes for Error 91

<table> <tr> <th>Cause</th> <th>Fix</th> </tr> <tr> <td>Uninitialized Variable</td> <td>Ensure to use Set to initialize the variable.</td> </tr> <tr> <td>Object Set to Nothing</td> <td>Check for Nothing before accessing the object.</td> </tr> <tr> <td>Object Creation Failure</td> <td>Implement error handling when creating objects.</td> </tr> <tr> <td>Incorrect References</td> <td>Validate that the object exists before using it.</td> </tr> <tr> <td>Late Binding Issues</td> <td>Prefer early binding for object declarations.</td> </tr> <tr> <td>Object Lifecycle Problems</td> <td>Manage scope and lifetime of objects effectively.</td> </tr> <tr> <td>Explicit Declaration without Initialization</td> <td>Declare and initialize in the same line where applicable.</td> </tr> </table>

<div class="faq-section"> <div class="faq-container"> <h2>Frequently Asked Questions</h2> <div class="faq-item"> <div class="faq-question"> <h3>What is Run-time Error 91?</h3> <span class="faq-toggle">+</span> </div> <div class="faq-answer"> <p>Run-time Error 91 occurs when you try to use an object variable that has not been set to an instance of an object in VBA.</p> </div> </div> <div class="faq-item"> <div class="faq-question"> <h3>How can I troubleshoot this error?</h3> <span class="faq-toggle">+</span> </div> <div class="faq-answer"> <p>You can troubleshoot by checking for uninitialized variables, validating object references, and implementing error handling in your code.</p> </div> </div> <div class="faq-item"> <div class="faq-question"> <h3>Is there a way to prevent Run-time Error 91?</h3> <span class="faq-toggle">+</span> </div> <div class="faq-answer"> <p>Yes, by initializing all object variables, using error handling, and ensuring valid references, you can prevent this error.</p> </div> </div> <div class="faq-item"> <div class="faq-question"> <h3>Can I fix Run-time Error 91 without coding experience?</h3> <span class="faq-toggle">+</span> </div> <div class="faq-answer"> <p>It may be challenging to fix without coding experience, but understanding the object model and referencing basics can help.</p> </div> </div> </div> </div>

To wrap it up, understanding and addressing Run-time Error 91 is crucial for anyone working with VBA and Excel. By being aware of the common causes and applying the suggested fixes, you can troubleshoot this error more effectively. Regular practice and experimentation with your code will also enhance your skills in handling errors like these.

<p class="pro-note">💡Pro Tip: Always validate object initialization before using them to avoid runtime errors!</p>