Text to Function definition

[necmik]

Is there a way to transform a text to function definition in M language? What I need is something like Function.From(text). For instance this text contains a function definition with empty body:
TextValue = "(InputColumn1 as text) as any => ..."

This one has 2 parameters:

TextValue = "(InputColumn1 as text, InputColumn2 as number) as any => ..."

I need to transfor this to function like adding a new column with function type:

FunctionAddedTable = Table.AddColumn(Source, "FunctionColumn", each [TextValue ])

[Anonymous]

The BIccountant has a great blog post on this with a custom fn for you to use.

Dynamically create types from text with Type.FromText in Power Query and Power BI (thebiccountant.co...

[AlexisOlson]

Yep. It looks like Expression.Evaluate is key here.

[necmik]

How can I use Expression.Evaluate here? I read the BIccountant blog. It gave me some idea but I couldn't figure out how to create a function from text. To be clear what I am trying to do is:

I have a table and this table has a column contains input schema as list of records:

{

  [name="InputColumn1", type="text"],

  [name="InputColumn2", type="number"]

}

My aim is to generate a function like this:

(InputColumn1 as text, InputColumn2 as number) as any => ...

[AlexisOlson]

Can you give an explicit example of input and expected output? I can't quite figure out exactly what part you're stuck on.

[necmik]

Actually I had given in my previous answer. My input is:

{

  [name="InputColumn1", type="text"],

  [name="InputColumn2", type="number"]

}

What I want as output is:

(InputColumn1 as text, InputColumn2 as number) as any => ...

(A function type)

[AlexisOlson · Accepted solution]

I was hoping for something I could paste into the Advanced Editor but I'll take a guess at what I think you mean.

Is this close to what you're after?

let
    Source = #table({"ListCol"},{{{[name="InputColumn1", type="text"],[name="InputColumn2", type="number"]}},{{[name="InputColumn1", type="text"]}}}),
    #"Added Custom" = Table.AddColumn(Source, "ToText", each "(" & Text.Combine(List.Transform([ListCol], each [name] & " as " & [type]), ", ") & ") as any => ""..."""),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "ToFunction", each Expression.Evaluate([ToText]))
in
    #"Added Custom1"

[necmik]

That is what I exactly want. I didn't expect Expression.Evaluate would be enough because of the word "Evaluate". Very thanks