SDWebImage doesn't work - swift

Question

What am I doing wrong? Everything runs but I don't get the Images, help! Thanks!
import UIKit
import Firebase
import FirebaseDatabase
import SDWebImage
struct postStruct {
let title : String!
let downloadURL : String!
}
class ZeroHomeViewController: UITableViewController {
var posts = [postStruct]()
override func viewDidLoad() {
super.viewDidLoad()
let ref = Database.database().reference().child("Posts")
ref.observeSingleEvent(of: .value, with: { snapshot in
print(snapshot.childrenCount)
for rest in snapshot.children.allObjects as! [DataSnapshot] {
guard let value = rest.value as? Dictionary<String,Any> else { continue }
guard let title = value["Title"] as? String else { continue }
guard let downloadURL = value["Download URL"] as? String else { continue }
let post = postStruct(title: title, downloadURL: downloadURL)
self.posts.append(post)
}
self.posts = self.posts.reversed(); self.tableView.reloadData()
})
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return posts.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell")
let imageView = cell?.viewWithTag(200) as! UIImageView
imageView.sd_setImage(with: URL(string: "downloadUrl"), placeholderImage: UIImage(named: "placeholder.png"))
let label1 = cell?.viewWithTag(1) as! UILabel
label1.text = posts[indexPath.row].title
return cell!
}
}

Answer 1

Secondly
Replace this line
imageView.sd_setImage(with: URL(string: "downloadUrl"), placeholderImage: UIImage(named: "placeholder.png"))
With this
imageView.sd_setImage(with: URL(string: "www.domain.com/url"), placeholderImage: UIImage(named: "placeholder.png"))
Make sure your edit the url to the image you want