Joomla 4 Plugin to overwrite value of a custom field

Question

I need a Joomla 4 Plugin to overwrite a marker in Custom Fields of type text or textarea with the article's title.

I added a onPrepareContent() method where I have access to the articles title as well as the custom field. Here is what I did so far:

class PlgContentMyReplacer extends CMSPlugin
{
    ...

    public function onContentPrepare($context, &$article, &$params, $page = 0)
    { 
        if(!in_array($context, array('com_content.article')))
        {
            return true;
        } 
            
        $article->jcfields[7]->value = str_replace('[LOCATION]', $article->title, $article->jcfields[7]->value); // This seems not to work
    
        return true; 
    }

    ...

}

$article->jcfields[7] is my custom field and [LOCATION] the marker I want to replace with the article's title.

This approach seems not to work. How can I overwrite the custom field's data before sending it to the browser?

Answer 1

I finally found the solution. I had to switch to a system Plugin. There inside the onAfterRender() function I can grab the whole body and the document title and replace the marker - like this:

public function onAfterRender()
{ 
    $body = $this->app->getBody();
    $document = $this->app->getDocument();
    $title = $document->getTitle();
        
    $body = str_replace('[LOCATION]', $title, $body);
    $this->app->setBody($body);

}