User-Defined Functions (UDFs) in Power Apps

User-defined functions (UDFs) are a new experimental feature in Power Apps that allow developers to write a formula once and reuse it multiple times throughout an app. This approach brings modularity, reusability, and cleaner formulas to Power Apps development.

Key Points

Reusable formulas: Write a formula once and call it wherever needed in your app.
Simplifies development: Reduces duplication and makes maintaining formulas easier.
Experimental feature: Currently in preview; intended for testing and learning purposes.

Caution

Since UDFs are not yet in the final release , they should not be used in production apps . Using them in critical applications could lead to unexpected behavior or compatibility issues. It's best to wait for the official release before leveraging this feature in production environments.

Enable the Power Apps User Defined Function (UDF) feature

Go to Settings
Upcoming features
Select Preview
Enable New Analysis Engine
Select Experimental
Enable User-defined functions
Once these features are enabled, save and refresh the application.

Creating and calling a Power Apps User-Defined Function (UDF)

Creating UDF

Goto App-Formulas

I have created a validateControls function that accepts a text parameter and returns a Boolean value indicating whether the input matches a specific pattern. In this example, the function allows only lowercase and uppercase letters; any other characters will cause it to return false.

  
    validateControls(controlValue: Text): Boolean = IsMatch(controlValue, "^[a-zA-Z]+$");

Syntax

FunctionName (Parameter1: DataType1, Parameter2: DataType2, ...): ReturnType = Formula

Calling UDF

Once created, you can call the UDF anywhere in your app. Here, we add a Textbox and a Label control to the screen and set the Text property of the label. The Label dynamically displays true and false based on input.

  
    "Text is valid: " & If(validateControls(TextInput1.Text), "true", "false")

Advantages of UDFs

Reusability: Write once, use everywhere.
Simplified maintenance: Change the formula in one place, update all usages.
Cleaner formulas: Avoid repeated nested If statements or complex logic.

Limitations

Still experimental ; may have bugs or breaking changes .
It cannot be used in production apps reliably yet.
Limited to Canvas apps (model-driven apps not supported yet).