swift and unexpectedly found nil while unwrapping an Optional value

问题

I have a class:

class ListOfEventsController: UIViewController, UITableViewDataSource, UITableViewDelegate {

and it contains a function:

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

    let cell = tableView.dequeueReusableCellWithIdentifier("CELL") as! SingleEventCell

and when I run it - it causes an error that says

fatal error: unexpectedly found nil while unwrapping an Optional value

but when I go to my story board I see:

and when I click CELL I see in its properties:

and also:

so the identifiers for CELL are set up, but I'm still getting this error.

What else can I do?

回答1:

1. In Storyboard select your prototype cell
2. alt + cmd + 4 to open the Attribute Inspector
3. Write CELL into the Identifier field.

Then try again ;)

回答2:

[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"CELL"];

For your problem.

回答3:

Try

let cell = tableView.dequeueReusableCellWithIdentifier("CELL", forIndexPath: indexPath) as! SingleEventCell

来源：https://stackoverflow.com/questions/35535791/swift-and-unexpectedly-found-nil-while-unwrapping-an-optional-value