SilverStripe renaming uploaded file only for specific field - silverstripe

Question

I have extended CMS settings to upload two CSS files. Part of the SiteConfig extension code -
<?php
//OTHER CODES HERE
$fields->addFieldToTab('Root.Main', $cssfile = UploadField::create(
'StyleSheet',
'Style Sheet'
));
$fields->addFieldToTab('Root.Main', $clientcssfile = UploadField::create(
'ClientStyleSheet',
'Client Style Sheet'
));
//OTHER CODES HERE
?>
And i have extended the File class
class FileRenameExtension extends DataExtension {
function onAfterUpload() {
$file = $this->owner;
$file->Name = 'CustomStyle.'.$file->getExtension();
$file->write();
}
}
PROBLEM
The code renames the file uploaded from all the fields, but I want to rename the files uploaded from ClientStyleSheet only.
Before it renames the file, if user uploads file with name that already exists, it warns, and if I click Overwrite, it overwrites the files and renames the file. I just want no matter what is the file name, it just saves the file with name that is specified in the File Extension Class
What is the proper way to rename file before its get uploaded?

Answer 1

You better use FileField directly in your case with custom upload() action handler.

Answer 2

With the DataExtension, you modify all instances of File, wherever they are uploaded.
One possible solution: You subclass File and hook into onAfterUpload:
class CSSFile extends File {
function onAfterUpload() {
$file = $this;
$file->Name = 'CustomStyle.'.$file->getExtension();
$file->write();
parent::onAfterUpload();
}
}
Now you use this in your SiteConfig, it should work with UploadField just like a standard File.
If I understand it correctly, you want to enable the user to add a stylesheet to the site. A different solution would then be to allow any filenames and to use the original filename in the template:
<link rel="stylesheet" href="$SiteConfig.StyleSheet.URL">
I would prefer to use this second solution.