UITableViewCell不显示

Question

i'm creating a simple Table but without storyboard, just coding, currently I can create the table but when I add the cell it crashes, these are my variables:

var optionsTableView:UITableView!
var options = ["Option1", "Option2"]

When I tapped a button the table appears, the function is:

@IBAction func Options(sender: AnyObject) {
    if optionsTableView != nil {
        optionsTableView.removeFromSuperview()
        self.optionsTableView = nil
        return
    }

    self.optionsTableView = UITableView()
    self.optionsTableView.backgroundColor = UIColor(white: 0, alpha: 0.95)
    self.optionsTableView.delegate = self
    self.optionsTableView.dataSource = self
    self.optionsTableView.translatesAutoresizingMaskIntoConstraints = false

    var constraints = [NSLayoutConstraint]()
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Leading, relatedBy: .Equal, toItem: self.view, attribute: .Leading, multiplier: 1.0, constant: 100.0))
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Trailing, relatedBy: .Equal, toItem: sender, attribute: .Trailing, multiplier: 1.0, constant: 0))
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Top, relatedBy: .Equal, toItem: sender, attribute: .Bottom, multiplier: 1.0, constant: 5.0))

    self.view.addSubview(optionsTableView)
    self.view.addConstraints(constraints)

    optionsTableView.addConstraints([NSLayoutConstraint(item: optionsTableView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .Height, multiplier: 1.0, constant: 220.0)])
}

The functions for the table:

func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return self.options.count
}

func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    return 44.0
}

Up to here everything goes well but with the cellForRowAtIndexPath the app crashes:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    var cell = optionsTableView.dequeueReusableCellWithIdentifier("cell")!
    if tableView == optionsTableView {
        cell = UITableViewCell(style: .Default, reuseIdentifier: "cell")
        cell.backgroundView = nil
        cell.backgroundColor = UIColor.clearColor()
        cell.textLabel?.textColor = UIColor.whiteColor()
        cell.textLabel?.text = self.options[indexPath.row]
        return cell
    }
    return cell
}

Specifically in this line the app crash:

var cell = optionsTableView.dequeueReusableCellWithIdentifier("cell")!

And console says: "fatal error: unexpectedly found nil while unwrapping an Optional value", what you think is happening??

Answer 1

That line is crashing is because it isn't finding a cell with that reuse identifier.

You have to register it:

self.tableView.registerClass(Cell.self as AnyClass, forCellReuseIdentifier: "cell")

That way when you force unwrap it won't crash.

Answer 2

I was a little changed your code. Fixed constraints.

import UIKit

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

var optionsTableView = UITableView()
var options = ["Option1", "Option2"]

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    optionsTableView = UITableView(frame: UIScreen.mainScreen().bounds)
    //optionsTableView.backgroundColor = UIColor(white: 0, alpha: 0.95)
    optionsTableView.delegate = self
    optionsTableView.dataSource = self
    optionsTableView.translatesAutoresizingMaskIntoConstraints = false

    view.addSubview(optionsTableView)
    optionsTableView.registerClass(UITableViewCell.classForCoder(), forCellReuseIdentifier: "cell")

}

override func viewWillLayoutSubviews() {

    var constraints = [NSLayoutConstraint]()
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Top, relatedBy: .Equal, toItem: topLayoutGuide, attribute: .Bottom, multiplier: 1.0, constant: 0))
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Bottom, relatedBy: .Equal, toItem: bottomLayoutGuide, attribute: .Top, multiplier: 1.0, constant: 0))
    constraints.append(NSLayoutConstraint(item: view, attribute: .Trailing, relatedBy: .Equal, toItem: optionsTableView, attribute: .Trailing, multiplier: 1.0, constant: 0))
    constraints.append(NSLayoutConstraint(item: optionsTableView, attribute: .Leading, relatedBy: .Equal, toItem: view, attribute: .Leading, multiplier: 1.0, constant: 0))

    view.addConstraints(constraints)
}


func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return self.options.count
}

func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    return 44.0
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let cell = optionsTableView.dequeueReusableCellWithIdentifier("cell")!
    cell.textLabel?.text = options[indexPath.row]
    return cell

}
}