REST Call to Post a Reply to a Discussion Board Topic w/o JSOM

Question

I am trying to find a way to post a reply to an existing discussion on a Discussion board using the REST API.

I cannot find a way to do this. I can only create a new discussion topic using REST. I have tried submitting a post request containing a ParentItemID in the body but that still creates a new discussion not a reply. Is there any way to do this using REST? The only examples I've seen use JSOM.

This is a similar question, but it got no responses.

Adding Discussion board replies using REST API

Answer 1

In fact ParentItemID property could not be specified since it is a read only property, it means the following query for creating a message (reply) item fails:

Url  /_api/web/lists/getbytitle('Discussions')/items
Method POST
Data { 
    '__metadata': { "type": "SP.Data.DiscussionsListItem" },
   'Body': "Message text goes here",  
   'FileSystemObjectType': 0, 
   'ContentTypeId': '<MessageContentTypeId>', 
   'ParentItemID': <DiscussionItemId>   //can't be set since it is read only
}  

Solution

For creating a message (reply) under a discussion item (folder) you could consider following solution: once message item is created, it's getting moved under a discussion item (folder container)

Example

The following example demonstrates how to create a message (reply) in Discussion Board via SharePoint REST API:

var listTitle = "Discussions"; //Discussions Board title
var webUrl = _spPageContextInfo.webAbsoluteUrl;
var messagePayload = {
   '__metadata': { "type": "SP.Data.DiscussionsListItem" },  //set DiscussionBoard entity type name
   'Body': "Message text goes here",  //message Body
   'FileSystemObjectType': 0, //set to 0 to make sure Message Item is created
   'ContentTypeId': '0x0107008822E9328717EB48B3B665EE2266388E', //set Message content type
   'ParentItemID': 123   //set Discussion item (topic) Id
};

createNewDiscussionReply(webUrl,listTitle,messagePayload)
.done(function(item)
{
    console.log('Message(reply) has been sent');
})
.fail(function(error){
    console.log(JSON.stringify(error));
});

where

function executeJson(options) 
{
    var headers = options.headers || {};
    var method = options.method || "GET";
    headers["Accept"] = "application/json;odata=verbose";
    if(options.method == "POST") {
        headers["X-RequestDigest"] = $("#__REQUESTDIGEST").val();
    }   

    var ajaxOptions = 
    {       
       url: options.url,   
       type: method,  
       contentType: "application/json;odata=verbose",
       headers: headers
    };
    if("data" in options) {
      ajaxOptions.data = JSON.stringify(options.data);
    }  

    return $.ajax(ajaxOptions);
}


function createListItem(webUrl,listTitle,payload){
    var url = webUrl + "/_api/web/lists/getbytitle('" + listTitle + "')/items";
    return executeJson({
        "url" :url,
        "method": 'POST',
        "data": payload
    });
}

function moveListItem(webUrl,listTitle,itemId,folderUrl){
    var url = webUrl + "/_api/web/lists/getbytitle('" + listTitle + "')/getItemById(" + itemId + ")?$select=FileDirRef,FileRef";
    return executeJson({
        "url" :url
    })  
    .then(function(result){
        var fileUrl = result.d.FileRef;
        var fileDirRef = result.d.FileDirRef;
        var moveFileUrl = fileUrl.replace(fileDirRef,folderUrl);
        var url = webUrl + "/_api/web/getfilebyserverrelativeurl('" + fileUrl + "')/moveto(newurl='" + moveFileUrl + "',flags=1)";
        return executeJson({
            "url" :url,
            "method": 'POST'
        });
     });
}


function getParentTopic(webUrl,listTitle,itemId){
    var url = webUrl + "/_api/web/lists/getbytitle('" + listTitle + "')/getItemById(" + itemId + ")/Folder";
    return executeJson({
        "url" :url,
    });
}


function createNewDiscussionReply(webUrl,listTitle, messagePayload){ 
    var topicUrl = null;
    return getParentTopic(webUrl,listTitle,messagePayload.ParentItemID)
    .then(function(result){
        topicUrl = result.d.ServerRelativeUrl;
        return createListItem(webUrl,listTitle,messagePayload);
    })
    .then(function(result){
        var itemId = result.d.Id;
        return moveListItem(webUrl,listTitle,itemId,topicUrl);
    });
}