Is it possible to provide a Select action Map from a parameter?

[biterbit]

I have a flow that processes a complex JSON array and uses the Select action to select parts of the array and reformat the data before passing it to PowerApps. I am finding that I am having to edit the Select action Map field frequently as I troubleshoot the flow and it occurred to me that it would be easier to pass in the map from an external source. But when I tried to pass in a string containing the map, it interpreted all the expressions as text and did not produce any useful output. If I paste the same content directly into the Map field (in Text mode) it works fine.

An example of the map content:

{"Version": "@item()['VersionLabel']","Modified": "@formatDateTime(convertFromUtc(item()['Modified'],'GMT Standard Time'), 'dd/MM/yyyy HH:mm')","ModifiedBy": "@item()['Editor']['LookupValue']","Name": "@item()['Title']","Code": "@item()['Code']"}

Is this a limitation of Power Automate that expressions cannot be passed to actions as parameters?

[ManishJain]

Hi @biterbit ,

Could you tell me what errors you are getting when you do so ? and why you need to edit again ?

Thanks

[biterbit]

@ManishJain Thanks for your response. At the moment I am just testing a solution to display previous versions of a list item in SharePoint, but I would like to develop a solution that would be usable across multiple tables. Because each table will have a different set of columns, I would like to be able to pass into the flow a mapping relating to the particular table structure that will be returned to the calling Power App. The rest of the flow I can make generic, but the mapping needs to be made variable rather than fixed and that's the bit I can't get to work.

I don't receive an error when I substitute the Map field text with a string variable, but instead of the data being returned I get the variable string. So, for example, using text in the Map field gives me:

[{"Version":"17.0","Modified":"10/11/2021 16:14","ModifiedBy":"User Name","Name":"Bedford","Code":"BED"},{"Version":"16.0","Modified":"10/11/2021 16:11".... etc

Using a string variable containing the same text returns:

[{"Version":"@item()['VersionLabel']","Modified":"@formatDateTime(convertFromUtc(item()['Modified'],'GMT Standard Time'), 'dd/MM/yyyy HH:mm')","ModifiedBy":"@item()['Editor']['LookupValue']","Name":"@item()['Title']","Code":"@item()['Code']"},{"Version":"@item()['VersionLabel']","Modified":"@formatDateTime... etc

I hope that explains things better.

[alex_mcla]

@biterbit did you solve this in the end? I have the same issue.

[biterbit]

@alex_mcla I could not find a way to get Power Automate to recognise the schema when presented as a string. In the end I took another approach and generated the schema for each table that I needed and copied it into the flow, and used a Switch action to choose the right schema. Far less efficient than what I wanted, but it works.

[MasterRA]

I have the same problem but I give a clearer context, I have more than 20 columns that I have to change their data source (also I use the xpath function to do a join between two data tables); copy the map I had and edit it column by column in a text editor but when pasting, it detects it as plain text and ignores the expressions that are included, the message that appears in the Map text box of the Select says " Enter a valid json" but what I don't understand is that when I copy the map from another "Select" and paste it into the one I'm editing, it does recognize all the expressions.

Why does text copied from a map formed by pasting recognize the expressions but text that was copied from the same source, edited in a text editor and pasted does not recognize the same expressions?

[NGS2410]

Same problem here. Power Automate do not recognize the expressions when they come in a variable. 
If a put the json in the text editor of the Map property it works fine, but if I use a variable it does not. 
I think this is a big issue. I ended using a lot of magical replace functions manipulating the array as a string to do a batch post. It was impossible to use a for each loop, since it take days to create thousands of records in Dataverse.

[miketl]

I was able to do this through a series of steps that essentially converts the data to XML, selects the desired nodes via xpath(), and then converting the resulting XML back to an object via json(). It can be done in 2 steps (a simple select and an elaborate compose), but I will describe it below in a series of smaller steps. Notably, this does not require a performance-sapping Apply-to-each loop. 🙂

In my case, I had an array of objects (call them field descriptor objects) that contain data about the properties I want to retain from a target object. All other properties on the target object needed to be removed.

Assume you have 2 variables: (1) 'fields', the array of field descriptor objects, each containing an InternalName property (since in my scenario the data came from a SharePoint list) which names a property on the target object that should be retained, and (2) 'target', the target object.

Create the xpath expression:

1: [Select] Create xpath node selectors: Make a select action that takes variables('fields') as input and maps 'path' to /target/@{item()['InternalName']}.

2: [Compose] Build an XML-compatible object from the resulting array:

addProperty( json('{}'), 'root', addProperty( json('{}'), 'paths', body('1') ) )

3: [Compose] Create the xpath expression (using xpath()) :

join( xpath( xml( outputs('2') ), '/root/paths/path/text()' ), '|' )

Get the nodes we're interested in keeping from the target object:

4: [Compose] Convert the target object to XML:

xml( addProperty( json('{}'), 'target', variables('target') ) )

5: [Compose] Extract the nodes we want to keep:

xpath( outputs('4'), outputs('3') )

6: [Compose] Create an XML-compatible object from the extracted nodes:

xml( concat( '<root>', join( outputs('5'), '' ), '</root>' ) )

Profit:

7: [Compose] Extract the final object:

json( outputs('6') ).root

I hope this helps. If there is an easier way, please share!