Facebook Graph API: How To Publish Text To Page, Including Image Attachment? - facebook-graph-api

Question

The documentation gives an example of how to upload an image, not via url, but as an attachment:
https://developers.facebook.com/docs/messenger-platform/reference/attachment-upload-api
curl -F "message={'attachment':{'type':'image', 'payload':{'is_reusable':true}}}" -F "filedata=#square.png;type=image/png" "https://graph.facebook.com/v2.12/1843037429354999/photos?access_token=<ACCESS_TOKEN>"
This leads to the following request:
POST https://graph.facebook.com/v2.12/<MY_PAGE_ID>/photos?access_token=<MY_ACCESS_TOKEN> HTTP/1.1
Host: graph.facebook.com
User-Agent: curl/7.52.1
Accept: */*
Content-Length: 2833
Expect: 100-continue
Content-Type: multipart/form-data; boundary=------------------------c71046aadf1a4e33
--------------------------c71046aadf1a4e33
Content-Disposition: form-data; name="message"
{'attachment':{'type':'image', 'payload':{'is_reusable':true}}}
--------------------------c71046aadf1a4e33
Content-Disposition: form-data; name="filedata"; filename="square.png"
Content-Type: image/png
<IMAGE_DATA>
--------------------------c71046aadf1a4e33--
However, this example does not work as advertised. The json object in the message parameter is literally posted as text in the post.
I'd like to be able to send along json post data that includes a 'message' and a 'access_token', so that I don't have to include the access token in the url.
How can I ensure that the type/image/payload json object is applied as a configuration, rather than used as the literal post message?
And how can I send along 'message' and 'access_token' in the postdata?

Answer 1

Found the solution.
This command...
curl -F "access_token=<MY_ACCESS_TOKEN>" -F "message=This is the message I wanna post." -F "filedata=#square.png;type=image/png" "https://graph.facebook.com/v2.12/<MY_PAGE_ID>/photos"
Gives this working request:
POST https://graph.facebook.com/v2.12/<MY_PAGE_ID>/photos HTTP/1.1
Host: graph.facebook.com
User-Agent: curl/7.52.1
Accept: */*
Content-Length: 3077
Expect: 100-continue
Content-Type: multipart/form-data; boundary=------------------------e94f377a15b0500f
--------------------------e94f377a15b0500f
Content-Disposition: form-data; name="access_token"
<MY_ACCESS_TOKEN>
--------------------------e94f377a15b0500f
Content-Disposition: form-data; name="message"
This is the message I wanna post.
--------------------------e94f377a15b0500f
Content-Disposition: form-data; name="filedata"; filename="square.png"
Content-Type: image/png
<IMAGE_DATA>
--------------------------e94f377a15b0500f--
All of a sudden it dawned on me. If the 'message' parameter posts a message, then why not simply put the message I want to post in there. Might as well include 'access_token' then, too. And it worked.
Instead of the deprecated 'message', you can also use 'caption' and it will also work.
Anyway, I can now attempt to reproduce this http request from C#. Glad I found this, because it saves me the effort from having to install the Facebook PHP SDK just to see how such a request should be formed.
(Why is there so little Facebook Graph API C# support, anyway?)
I still have no idea how to properly send along the attachment/type/image/payload json object from Facebook's documentation, though.
Oh, well.