如何在定义另一个实体属性时使用Entity属性

Question

I need to use a property in one of my entities to set the value of another property in that same entity.

Let me explain myself, i have two properties, one of them is the image name, and the other one is a download link, in order to get a download link i need to take the image name and pass it to a function that would get my download link from the web

I have been looking at the life cycle methods on doctrine, but i cant get it to work, at the moment i only want to dislay that image name into the download link property.

So, the user uploads a file, i get the name of the file back, i take that name and use it to fetch a download link within my download link property.

Im using the "PostPersist" method and again, its just returning a null value when i take a look at my DB

Entity:

/**
 * @ORM\Column(type="text", nullable=true)
 */
private $downloadImage;

//I commented out the setters and getters, cause i dont think i  
//need them since i will be setting the value by default in the
//"PostPersist" method            

PostPersist Method:

/**
* @ORM\PostPersist
*/
public function setDownloadLinkValue ()
{
    $this->downloadImage = $this->getImageName(); //Yes yes, i have tried both, with "getImageName()" and "imageName"
}

I think its a very silly error, but im not 100% sure, if you need something else to see in my code please let me know so i can update this post