SharePoint designer REST call to populate lookup field in SharePoint 2013 list

Question

I'm trying to update a multi-value lookup field in a SharePoint 2013 list from a SharePoint designer workflow using the 'Call HTTP Web Service' action.

Here's how the field looks when querying a list item with two values:

    "Assigned_x0020_toId":{"__metadata":{"type":"Collection(Edm.Int32)"},"results":[1,2]}

I'm using nested dictionaries to create the json structure for the POST request within SharePoint Designer but I'm not sure how to create a JSON array as needed by the "results" field.

I'm reading the "Assigned to" field from another list into a workflow variable typed as "Lookup Ids, comma delimited".

I then create a dictionary with an item "results" and the value set to my comma delimited lookup ids variable.

The json this produces is:

    "Assigned_x0020_toId":{"results":1}

I get the following error when executing the query:

An unexpected 'PrimitiveValue' node was found when reading from the JSON reader. A 'StartArray' node was expected.

I think that's because the query should be:

    "Assigned_x0020_toId":{"results":[1]}

Can anybody help me achieve that in SharePoint designer or suggest a better alternative?

The reason I'm using the web service is that I'm trying to create a workflow that loops through all of a list's items updating values when changes are made in another list.

Answer 1

I know it's been some time, but here's how you can build this in SharePoint Designer:

1. Start with a string, and set it to the array you want. (i.e. thisArray, type String, value [1])

2. Then Build a Dictionary as a single item. (i.e. thisDictionary, type Dictionary; Add results, type Dictionary, value Variable:thisArray. SPD will default the "Return field as" to "As Dictionary from JSON")

3. In your payload dictionary, assign Assigned_x0020_toId, type Dictionary, value thisDictionary.