Q:

initialize tinymce with content

I have a page containing one tinymce4 editor instance. I want to initialize this editor with some content, programmatically. I know that I have to call: tinymce.get('editor').setContent('my content'); 
However I have trouble to do this when tinymce is getting initialized. This question has already been asked: initialize tinyMCE with default content but the answer that was given at that time is not working, at least for tinymce4. 
Here is what I have tried:
1st attempt:
    tinymce.init({
      mode: "textareas",
      ...
      setup: function (editor) {
         ...
         editor.setContent('my content');
      }
   });

-> Uncaught TypeError: Cannot read property 'body' of undefined
2nd attempt:
    tinymce.init({
      mode: "textareas",
      ...
    };
    tinymce.get('editor').setContent('my content');

-> Uncaught TypeError: Cannot read property 'setContent' of null 
(however if I do this when the page containing the tinymce editor has already been loaded, it works).
3rd attempt (SO 12083361 answer):
$(document).ready(function(){
    tinymce.get('editor').setContent('my content');
});

-> Uncaught TypeError: Cannot read property 'setContent' of null 
All this fails with tinymce.activeeditor.setContent('my content'); as well.
Where should I place tinymce.get('editor').setContent('my content');in my code to have it working ?

A:

With version 4 you should do it like this:
tinymce.init({selector:'textarea'});
tinymce.activeEditor.setContent('custom');

Here's a fiddle.

