Copy field value text to $Content field on page save Silverstripe 3

Question

I want to copy text from another html5editorfield to $Content a page publish. what i have is below:

public function onBeforeWrite()
{
    $searchableContent = $this->ContentBeforeSections();      
    $this->setField('Content', $searchableContent);
    parent::onBeforeWrite();
} 

not sure what to try, I also have "heyday/silverstripe-versioneddataobjects" addon. Any ideas are helpful