UDF: can we pass a column as parameter?

[Marcl4]

Dear gents,

I'm converting a normal measure to a UDF... and I have a challenge passing a column name as parameter?

My measure should become

Sub_UDF = "Countries: " & pbi.Subtitle(FACT_ITA, DIM_Geo[CountryName],8)

and I get an error Function SUMMARIZE expects a column name as argument number 2.

(tried putting VALUES, SELECTEDVALUES around the column name without success!)
Does it exist a solution or can't it be solved?

The beginning of the UDF looks like that, and we find the SUMMARIZE with a column name as second parameter

DEFINE

    FUNCTION pbi.Subtitle = (

        SourceTable : table expr,

        SourceColumn : expr,

        MaxItems : scalar

    )

    =>

        VAR BaseTable =

            FILTER(

                SUMMARIZE(

                    SourceTable,

                    SourceColumn,

                    "Cnt", [#Projects]

                ),

                [Cnt] > 0

            )

[v-priyankata]

Hi @Marcl4 

Thank you for reaching out to the Microsoft Fabric Forum Community.

@Kedar_Pande @rohit1991 @xifeng_L Thanks for your inputs

I hope the information provided by users was helpful. If you still have questions, please don't hesitate to reach out to the community.

[Kedar_Pande]

@Marcl4 

Workarounds:

1. Create separate UDFs for each column:

pbi.SubtitleCountry = pbi.Subtitle(FACT_ITA, DIM_Geo[CountryName], 😎
pbi.SubtitleRegion = pbi.Subtitle(FACT_ITA, DIM_Geo[RegionName], 😎

2. Use Field Parameters to pass column names (not supported in UDFs yet).

3. Rewrite as regular measure with SWITCH:

Sub_UDF =
SWITCH(
SELECTEDVALUE(ColumnSelector[ColumnName]),
"Country", "Countries: " & pbi.SubtitleCountry(FACT_ITA, 8),
"Region", "Regions: " & pbi.SubtitleRegion(FACT_ITA, 8),
BLANK()
)

If this answer helped, please click Kudos or Accept as Solution.
-Kedar
LinkedIn: https://www.linkedin.com/in/kedar-pande

[xifeng_L]

Hi @Marcl4  

You used the wrong parameter type. Pls change the type of SourceColumn to anyref, as below:

DEFINE
    FUNCTION pbi.Subtitle = (
        SourceTable : table expr,
        SourceColumn : anyref,
        MaxItems : scalar
    )
    =>
        VAR BaseTable =
            FILTER(
                SUMMARIZE(
                    SourceTable,
                    SourceColumn,
                    "Cnt", [#Projects]
                ),
                [Cnt] > 0
            )

Did I answer your question? If yes, pls mark my post as a solution and appreciate your Kudos !

Thank you~

[rohit1991]

Hii @Marcl4 

In DAX UDFs you cannot pass a column reference as a parameter.
UDF parameters only accept expressions, not real column metadata, so functions like SUMMARIZE, GROUPBY, SELECTCOLUMNS, etc. cannot use a parameter in place of a column name. This is a current limitation of DAX: column arguments must be hard-coded inside the function body.

To achieve dynamic behavior, you must either:

• write separate UDFs for each column, or

• redesign the logic to work on values (e.g., using VALUES() or SELECTEDVALUE()), not structural column references.

There is no workaround today to dynamically inject a column into SUMMARIZE via a UDF parameter.