Set AssignedToId for a ListItem using SharePoint 2013 Rest API.

Hi,

Was working on a requirement in which we had to create new listitems of task type and set the Assigned To field in it.

It wasn’t as straight forward as we thought. Finally this is what worked

var fieldUserValues = new Array();
 fieldUserValues.push(userIdForTask);

var item = {
 "__metadata": { "type": eventToSave.TaskTypeName },
 "Title": eventToSave.EventName,
 "StartDate": startDate,
 "DueDate": endDate,
 "Body" : eventToSave.Description,
 "Priority": eventToSave.TaskPriority,
 'AssignedToId': { "results": fieldUserValues },
 };
 executor.executeAsync(
 {
 url: appweburl + "/_api/SP.AppContextSite(@target)/web/lists/getbytitle('" + eventToSave.TaskName + "')/items?@target='" + hostweburl + "'",
 method: "POST",
 headers: {
 "accept": "application/json;odata=verbose",
 "content-type": "application/json;odata=verbose",
 "X-RequestDigest": $("#__REQUESTDIGEST").val()

 },
 body: JSON.stringify(item),
 success: function (data) { succeededInsert(data); },
 error: failedInsert
 }
 );

Hope it helps.