Power Query Custom Function Text List Argument in Parameter List RRS feed

  • Question

  • After review the Power Query Formula Language Specification I'm a bit confused on how to specify a text list argument in a custom function's parameter list.  I've tried this ... 

    (optional My_List as {text}) =>

    ... however, Power Query doesn't "like" it.  Any pointers?

    Tuesday, November 11, 2014 2:52 PM


  • According to section 5 of the language spec, this is not possible:

    "Note that the is and as operators only accept primitive types as their right operand. M does not provide means to check values for conformance to custom types."

    • Proposed as answer by Curt Hagenlocher Tuesday, November 11, 2014 9:56 PM
    • Marked as answer by Mark Weisman Tuesday, November 11, 2014 9:57 PM
    Tuesday, November 11, 2014 9:56 PM