Type.FunctionRequiredParameters

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Type.FunctionRequiredParameters is a Power Query M function that determines the minimum number of parameters required to invoke the input function type. The function returns a number indicating the minimum required parameters for the given function type.

Compatible with: Power BI Service Power BI Desktop Excel Microsoft 365

Syntax

Type.FunctionRequiredParameters( type as type ) as number

Description

The Type.FunctionRequiredParameters function is used to identify the minimum number of parameters necessary for invoking a specific function type. The function takes a type value as input and returns a number indicating the number of required parameters. The function accepts both custom types and library functions.

Examples

Let’s say you want to find the required number of parameters for a function like Text.Combine. This function requires 2 parameters and none are optional. The following statement returns the number of required parameters:

// Output: 2
Type.FunctionRequiredParameters( Value.Type( Text.Combine ) )

If you’re dealing with a function that has both required and optional parameters, the function only returns the number of required fields. For example, the Date.FromText function takes 2 arguments, one is required and the other is optional.

// Output: 1
Type.FunctionRequiredParameters( Value.Type( Date.FromText ) )

To return the total number of parameters instead, you can combine the Record.FieldCount and Type.FunctionParameters function:

// Output: 2
Record.FieldCount( 
  Type.FunctionParameters( Value.Type( Date.FromText ) ) 
)

Instead of retrieving the type of a library function, you can also provide a custom data type as input. The following statement returns the required number of parameters of such a custom type:

// Output: 1
let
  customType = type function ( x as logical, optional y as date) as date,
  requiredParameters = Type.FunctionRequiredParameters( customType  )
in
  requiredParameters

Other functions related to Type.FunctionRequiredParameters are:

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Microsoft documentation: https://learn.microsoft.com/en-us/powerquery-m/type-functionrequiredparameters