ApexからChatterに投稿する

ちょうど、質問があって回答がされていたので忘れないように記録しておきます。

How to Create chatter post and mention user in chatter post using Apex class?

//Adding a Text post
FeedItem post = new FeedItem();
post.ParentId = oId; //eg. Opportunity id, custom object id..
post.Body = 'Enter post text here';
insert post;

//Adding a Link post
FeedItem post = new FeedItem();
post.ParentId = oId; // Record Id eg. Opportunity id, custom object id..
post.Body = 'Enter post text here';
post.LinkUrl = 'http://www.infallibletechie.com';
insert post;

//Adding a Content post
FeedItem post = new FeedItem();
post.ParentId = oId; // Record Id eg. Opportunity id, custom object id..
post.Body = 'Enter post text here';
post.ContentData = base64EncodedFileData;
post.ContentFileName = 'infallible.pdf';
insert post;