Simple stretchy header example for Swift.

stretchy_header.swift

//
//  ViewController.swift
//  stretchy header example
//
//  Created by Alex on 07/03/2018.
//  Copyright © 2018. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIScrollViewDelegate {
    
    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var tableView: UITableView!
    
    let STATUS_BAR_HEIGHT: CGFloat = 20.0
    let MAX_HEIGHT_HEADER: CGFloat = 300.0
    let MIN_HEIGHT_HEADER: CGFloat = 64.0

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        tableView.contentInset = UIEdgeInsets(top: MAX_HEIGHT_HEADER - STATUS_BAR_HEIGHT, left: 0, bottom: 0, right: 0)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        let y = -scrollView.contentOffset.y
        let height = min(max(y, MIN_HEIGHT_HEADER), MAX_HEIGHT_HEADER)
        imageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: height)
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 40
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return UITableViewCell()
    }

}