How do I send data to a lookup field with ReST? SP2013

Question

I've been working with a jQuery AJAX call to post data to one of my SharePoint lists.

One of the fields in this list is a look-up field. In forming my JSON data to push to the list I was able to push data to each field with the exception of the look-up field.

How do I push data into a lookup field?

I know I need to push the target list's ID to the look-up field, but have gotten hung up on just how to format the data.

Answer 1

Here is an example from this question:Updating Lookup Values with the REST API

var call = jQuery.ajax({
        url: _spPageContextInfo.webAbsoluteUrl +
            "/_api/Web/Lists/getByTitle('Sales Opportunities')/Items(5)",
        type: "POST",
        data: JSON.stringify({
            "__metadata": { type: "SP.Data.Sales_x0020_OpportunitiesListItem" },
            StateId: 2
        }),
        headers: {
            Accept: "application/json;odata=verbose",
            "Content-Type": "application/json;odata=verbose",
            "X-RequestDigest": jQuery("#__REQUESTDIGEST").val(),
            "IF-MATCH": item.__metadata.etag,
            "X-Http-Method": "PATCH"
        }
    });