How to use the Implements in Excel VBA

📝 Tech Talk: Using Implements in Excel VBA

✨ Hey there tech enthusiasts! 👋 In this blog post, we will dive into the world of Implements in Excel VBA and how they can help you implement shapes for your engineering projects. We'll address some common issues and provide easy solutions so you can create a generalizable program. Let's get started! 🚀

🔢 Understanding the Problem Our friend here wants to create an interface called "cShape" and have the "cRectangle" and "cCircle" classes implement it. However, they encountered a Compile Error when running their test cases. Let's see what might be causing this error and how we can fix it! 🛠️

🐠 The Compile Error The Compile Error thrown states, "Object module needs to implement '' for interface ''." This error usually occurs when the class doesn't fully implement the interface members defined in the interface module. We need to make sure that every member in the interface is implemented by the classes that are supposed to implement it. 🐛

📋 Solution: Complete Implementation To resolve this error, we need to ensure that each member of the "cShape" interface is implemented correctly in the "cRectangle" and "cCircle" classes. Here's what the corrected code should look like:

💠 cShape interface

Option Explicit

Public Function getArea()
End Function

Public Function getInertiaX()
End Function

Public Function getInertiaY()
End Function

Public Function toString()
End Function

💠 cRectangle class

Option Explicit
Implements cShape

Public myLength As Double
Public myWidth As Double

Public Function cShape_getArea() As Variant
    cShape_getArea = myLength * myWidth
End Function

Public Function cShape_getInertiaX() As Variant
    cShape_getInertiaX = (myWidth) * (myLength ^ 3)
End Function

Public Function cShape_getInertiaY() As Variant
    cShape_getInertiaY = (myLength) * (myWidth ^ 3)
End Function

Public Function cShape_toString() As Variant
    cShape_toString = "This is a " & myWidth & " by " & myLength & " rectangle."
End Function

💠 cCircle class

Option Explicit
Implements cShape

Public myRadius As Double

Public Function cShape_getArea() As Variant
    cShape_getArea = Application.WorksheetFunction.Pi() * (myRadius ^ 2)
End Function

Public Function cShape_getInertiaX() As Variant
    cShape_getInertiaX = Application.WorksheetFunction.Pi() / 4 * (myRadius ^ 4)
End Function

Public Function cShape_getInertiaY() As Variant
    cShape_getInertiaY = Application.WorksheetFunction.Pi() / 4 * (myRadius ^ 4)
End Function

Public Function cShape_toString() As Variant
    cShape_toString = "This is a radius " & myRadius & " circle."
End Function

🎉 Understanding the Solution In the solution above, notice that we have prefixed the interface members' names with cShape_ in the implementing classes. This ensures that the classes correctly implement the interface. By doing so, we avoid the Compile Error and achieve the desired behavior.

⚡ Final Thoughts: Calibrate Your Implementation Remember, whenever implementing an interface in Excel VBA, ensure that all interface members are implemented in the classes that implement it. This helps avoid compile errors and ensures seamless functionality. 🙌

💌 If you found this post helpful, share it with your fellow Excel enthusiasts! 💪 And don't forget to leave your thoughts and questions in the comments below. Let's excel together! 😄✨