Can't set default variable value for Data Type parameter in custom functions

[bob-reus]

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Current Behavior

When I create a custom function that takes a Data Type parameter, I can't set a default value when calling that function.

Likewise, I can't set an initial value for a custom Data Type page state. I assume these two issues are related or have the same cause.

Expected Behavior

I expect to be able to set a default value (or initial value for page states) for custom Data Type parameters, just like I can with other types.

Steps to Reproduce

1. Create custom Data Type
2. Create custom function that takes this custom Data Type as a parameter
3. Call custom function in a widget (for example to display the output of the function as text)
4. Observe that there is no field to set a variable default value

or

1. Create custom Data Type
2. Create a new page
3. Add a page state with the Data Type created in Step 1
4. Observe there is no field to set an initial value

Reproducible from Blank

• The steps to reproduce above start from a blank project.

Bug Report Code (Required)

IT4sl8j1vJN1pbwA1aqJdcBr/TkRJW4iR5EWsct/cxQcB4j4O7QDdeDCRBNvZ72zaH9UHWeZkk4J//THjYXxIcdfPUisbN1/1LlUYBPPbGCtMLaSC7mOfXB5I8VjCmnF0quj2CVCKs12c0IM2nGAPN68Yz6Cf9qOYwx5e6fDbOY=

Visual documentation

A double parameter, which accepts a default variable value:

A custom Datatype parameter, where this field is missing:

An integer page state, where I can set an initial value:

A custom Datetype page state, where this field is missing:

Environment

- FlutterFlow version: v6.3.41 released October 7, 2025
  Flutter version is 3.32.4
- Platform: any

Additional Information

In some cases the datatype isn't available on the first call of the function, which leads to red screens and null check errors.

In the case of page states, this leads to null check errors as well, if I need the page state to have a value on loading the page. Setting a value in an action on page load still leads to a short flash or a null check error related red screen.

[Alezanello]

When you set a DataType, you need to initialize it first — that’s where the values are applied.

For example, if you have a DataType called MMSS that contains two integer fields (minutes and seconds), you can:

• Create and assign its values directly, or
• Initialize it when the component loads (e.g., using actions to set it on a component state variable) and then use it in your custom function.

Currently, those default values are explicitly defined in the DataType settings.

[bob-reus]

These Data Types do get initialized and assigned with an action at page load, and even with the defaults set, I get null check error red screens. I would have liked behavior that's consistent with other types.

[Alezanello]

In that case, you might already have an AppState of that DataType with initialized values. You can use it directly and simply update the values when needed to avoid performing null checks.

[github-actions]

This issue is stale because it has been open for 7 days with no activity. If there are no further updates, a team member will close the issue.

[Alezanello]

Closing this issue since we haven't heard back from you. If you are still facing the problem please submit a new issue. Thank you!