I am trying to add an option to add images to blog posts. Have used the post here http://www.ssbits.com/tutorials/2011/adding-an-image-to-a-blog-post-using-decorators-and-the-silverstripe-blog-module/

I have changed the code as per ss3 requirements yet I don't see upload image option when creating a new blog post.
Created a file BlogEntryDecorator.php inside mysite/code like:

<?php
class BlogEntryDecorator extends SiteTreeDecorator {

	static $has_one = array(
		'BlogImage' => 'Image'
	);

	public function getCMSFields() {
		$fields = parent::getCMSFields();
		$fields->addFieldToTab("Root.Images", new UploadField('BlogImage'));
		return $fields;
	}
}

and then in mysite/_config.php added the following line:

DataObject::add_extension('BlogEntry', 'BlogEntryDecorator');

Kindly suggest as to how can I make this work

<?php
#-------------------------------------------------------------
# Silverstripe v3.0.2 BlogEntry Upload Image
# Create file: mysite/code/ext/BlogEntryDecorator.php
#-------------------------------------------------------------
class BlogEntryDecorator extends DataExtension {

static $has_one = array(
'BlogImage' => 'Image'
);

public function updateCMSFields(FieldList $fields) {
parent::updateCMSFields($fields);
$fields->addFieldToTab("Root.Main", $BlogImage = new UploadField('BlogImage'), 'Content');
$BlogImage->getValidator()->setAllowedExtensions(File::$app_categories['image']);
}

}
?>

<?php
#-------------------------------------------------------------
# Edit file: mysite/code/_config.php
#-------------------------------------------------------------
Object::add_extension('BlogEntry', 'BlogEntryDecorator');
?>

Greatly appreciated, this update to SS 3.0.x. The SSbits entry (see above) is no longer up to date and generates an error.

Don't forget to adjust \blog\templates\Includes\BlogSummary.ss, for example:

<% if BlogHolder.ShowFullEntry %>
$Content
<% else %>
<% if BlogImage %>
<div class="captionImage left" style="width: 200px;">
<% with BlogImage %>$CroppedImage(200,133)<% end_with %>
</div>
<% end_if %>
<% control Content %>$Summary.NoHTML<% end_control %>
<a href="$Link" title="<% _t('VIEWFULL', 'View full post: ') %> '$Title'">Read more...</a></p>
<% end_if %>