Chatter (publisher) canvas app: multisegment feed post?

Question

In my canvas app, I can easily post to a chatter feed in this way:

Sfdc.canvas.client.subscribe(sr.client,
{
  name: "publisher.getPayload", onData: function (event)
  {
    var post = {};

    post.feedItemType = "LinkPost";
    post.url = url;
    post.urlName = urlName;

    Sfdc.canvas.client.publish(sr.client,
      { name: "publisher.setPayload", payload: post });
  }
});

- this posts a link item.

But how do I post a multisegment item? Apex/SOAP/REST API documentation segments of Salesforce.com have examples of posting such items; but is it possible with a simple Canvas API?

My ultimate goal is to post a text+link+inline image item, as Salesforce doesn't allow to attach preview images to link items (except for some of the whitelisted content providers).

Thank you in advance.

Answer 1

I found the following in Posting to a Chatter Feed using the Cross-Domain XHR client side proxy support.

var sr = JSON.parse('<%=signedRequestJson%>');
// Reference the Chatter user's URL from Context.Links object.
var url = sr.context.links.chatterFeedsUrl+"/news/"+sr.context.user.userId+"/feed-items";
var body = {body : {messageSegments : [{type: "Text", text: "Some Chatter Post"}]}};

Sfdc.canvas.client.ajax(url,
    {client : sr.client,
        method: 'POST',
        contentType: "application/json",
        data: JSON.stringify(body),
        success : function(data) {
        if (201 === data.status) {
             alert("Success");
             }
        }
    });

Of note is how it does a more RAW AJAX POST to via the Canvas API in JavaScript.

With this, the problem is how to do a multipart/form-data POST via the Canvas ajax method. The Chatter API: Examples, Best Practices and Tips links to an example multipart POST.

The source for the Canvas ajax method is on GitHub.

Try switching out the JSON.stringify(body) with the FormData instance.

At a very high level:

1. Add the first FormData for the normal JSON body. Se the Content-Type to application/json. See Composing multipart/form-data with a different Content-Type on each parts with Javascript
2. Append the next FormData entry for the attachment with the correct Content-Type.
3. Use the FormData as the data parameter to the Ajax request.

---

From Sending multipart/formdata with jQuery.ajax:
I'm aware that a the jQuery ajax method is a very different thing to the canvas ajax method, but it might provide some clues in the right direction around using the FormData.

var data = new FormData();
jQuery.each(jQuery('#file')[0].files, function(i, file) {
    data.append('file-'+i, file);
});

jQuery.ajax({
    url: 'php/upload.php',
    data: data,
    cache: false,
    contentType: false,
    processData: false,
    type: 'POST',
    success: function(data){
        alert(data);
    }
});

Answer 2

It seems that currently the only way to make a multi-segment post is to use the REST API. I've created a post on IdeaExchange about supporting multi-segment posts with the regular canvas API, please vote for it:

https://success.salesforce.com/ideaView?id=0873A000000LmYRQA0