TableHeaderView-Höhe dynamisch einstellen

Meine Anwendung erstellt einen UITableViewController, der eine benutzerdefinierte tableHeaderView enthält, die eine beliebige Höhe haben kann. Ich habe Probleme damit, diesen Header dynamisch zu setzen, da die vorgeschlagenen Methoden diesen Header offenbar gekürzt haben. Der relevante Code meines UITableViewControllers:

import UIKit
import SafariServices

class RedditPostViewController: UITableViewController, NetworkCommunication, SubViewLaunchLinkManager {

    //MARK: UITableViewDataSource
    var post: PostData?
    var tree: CommentTree?
    weak var session: Session! = Session.sharedInstance

    override func viewDidLoad() {
        super.viewDidLoad()

        // Get post info from api
        guard let postData = post else { return }

        //Configure comment table
        self.tableView.registerClass(RedditPostCommentTableViewCell.self, forCellReuseIdentifier: "CommentCell")

       let tableHeader = PostView(withPost: postData, inViewController: self)
       let size = tableHeader.systemLayoutSizeFittingSize(UILayoutFittingExpandedSize)
       let height = size.height
       let width = size.width
       tableHeader.frame = CGRectMake(0, 0, width, height)
       self.tableView.tableHeaderView = tableHeader


       session.getRedditPost(postData) { (post) in
           self.post = post?.post
           self.tree = post?.comments
           self.tableView.reloadData()
       }
    }
}

Dies führt zu folgendem falschen Layout:

Wenn ich die Zeile ändere:tableHeader.frame = CGRectMake(0, 0, width, height) zutableHeader.frame = CGRectMake(0, 0, width, 1000) die tableHeaderView wird sich richtig anordnen:

Ich bin mir nicht sicher was ich hier falsch mache. Außerdem benutzerdefinierte UIView-Klasse, wenn dies hilft:

import UIKit
import Foundation

protocol SubViewLaunchLinkManager: class {
    func launchLink(sender: UIButton)
}

class PostView: UIView {

    var body: UILabel?
    var post: PostData?
    var domain: UILabel?
    var author: UILabel?
    var selfText: UILabel?
    var numComments: UILabel?

    required init?(coder aDecoder: NSCoder) {
        fatalError("Not implemen,ted yet")
    }

    init(withPost post: PostData, inViewController viewController: SubViewLaunchLinkManager) {
        super.init(frame: CGRectZero)

        self.post = post
        self.backgroundColor = UIColor.lightGrayColor()

        let launchLink = UIButton()
        launchLink.setImage(UIImage(named: "circle-user-7"), forState: .Normal)
        launchLink.addTarget(viewController, action: "launchLink:", forControlEvents: .TouchUpInside)
        self.addSubview(launchLink)

        selfText = UILabel()
        selfText?.backgroundColor = UIColor.whiteColor()
        selfText?.numberOfLines = 0
        selfText?.lineBreakMode = .ByWordWrapping
        selfText!.text = post.selfText
        self.addSubview(selfText!)
        selfText?.sizeToFit()

        //let attributedString = NSAttributedString(string: "Test"/*post.selfTextHtml*/, attributes: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType])
        //selfText.attributedText = attributedString

        body = UILabel()
        body!.text = post.title
        body!.numberOfLines = 0
        body!.lineBreakMode = .ByWordWrapping
        body!.textAlignment = .Justified
        self.addSubview(body!)

        domain = UILabel()
        domain!.text = post.domain
        self.addSubview(domain!)

        author = UILabel()
        author!.text = post.author
        self.addSubview(author!)

        numComments = UILabel()
        numComments!.text = "\(post.numComments)"
        self.addSubview(numComments!)

        body!.translatesAutoresizingMaskIntoConstraints = false
        domain!.translatesAutoresizingMaskIntoConstraints = false
        author!.translatesAutoresizingMaskIntoConstraints = false
        selfText!.translatesAutoresizingMaskIntoConstraints = false
        launchLink.translatesAutoresizingMaskIntoConstraints = false
        numComments!.translatesAutoresizingMaskIntoConstraints = false

        let views: [String: UIView] = ["body": body!, "domain": domain!, "author": author!, "numComments": numComments!, "launchLink": launchLink, "selfText": selfText!]
        //let selfTextSize = selfText?.sizeThatFits((selfText?.frame.size)!)
        //print(selfTextSize)
        //let metrics = ["selfTextHeight": selfTextSize!.height]

                   self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[body]-[selfText]-[domain]-|", options: [], metrics: nil, views: views))
       self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[body]-[selfText]-[author]-|", options: [], metrics: nil, views: views))
    self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[body]-[selfText]-[numComments]-|", options: [], metrics: nil, views: views))
    self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[launchLink]-[numComments]-|", options: [], metrics: nil, views: views))
    self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[body][launchLink]|", options: [], metrics: nil, views: views))
    self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[selfText][launchLink]|", options: [], metrics: nil, views: views))
    self.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[domain][author][numComments][launchLink]|", options: [], metrics: nil, views: views))
}

override func layoutSubviews() {
    super.layoutSubviews()
    body?.preferredMaxLayoutWidth = body!.bounds.width
}
}