为什么Executor接口没有一个将Callable作为参数的方法？(Why Executor interface doesn't have a method, which takes Callable as a parameter?)

 设置你的单元格标识符选择你的单元格，然后你会在Attributes Inspector看到Identifier字段，在那里设置你的重用标识符......就是这样。 
 
 另请尝试添加： - 
 
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}
 
 并更换 
 
 let cell = tableView.dequeueReusableCellWithIdentifier("contactDetail") as! ContactDetailTableViewCell
 
 至 
 
let cell = tableView.dequeueReusableCellWithIdentifier("contactDetail", forIndexPath: indexPath) as! ContactDetailTableViewCell
 
 
 说明 
 
 CMD + CLICK上的函数名称： dequeueReusableCellWithIdentifier - 您将被引导到它的文档.. 
 
public func dequeueReusableCellWithIdentifier(identifier: String) -> UITableViewCell? // Used by the delegate to acquire an already allocated cell, in lieu of allocating a new one.
@available(iOS 6.0, *)
public func dequeueReusableCellWithIdentifier(identifier: String, forIndexPath indexPath: NSIndexPath) -> UITableViewCell // newer dequeue method guarantees a cell is returned and resized properly, assuming identifier is registered
 
 
 
 dequeueReusableCellWithIdentifier(identifier: String, forIndexPath indexPath: NSIndexPath)保证你有一个单元格.. 
 
 
 也许这些链接是有帮助的： - 
 
 致命错误：在解包可选值时意外发现为零 
 
 https://stackoverflow.com/a/25569704/6297658 

To set your cell identifier Select your cell then you will see Identifier field in Attributes Inspector, set your reuse identifier there... That's about it..
 
Also try adding :- 
 
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}
 
and replace 
 
 let cell = tableView.dequeueReusableCellWithIdentifier("contactDetail") as! ContactDetailTableViewCell
 
to
 
let cell = tableView.dequeueReusableCellWithIdentifier("contactDetail", forIndexPath: indexPath) as! ContactDetailTableViewCell
 
 
EXPLANATION
 
CMD+CLICK on the function Name : dequeueReusableCellWithIdentifier-- you will be directed to its documentation ..
 
public func dequeueReusableCellWithIdentifier(identifier: String) -> UITableViewCell? // Used by the delegate to acquire an already allocated cell, in lieu of allocating a new one.
@available(iOS 6.0, *)
public func dequeueReusableCellWithIdentifier(identifier: String, forIndexPath indexPath: NSIndexPath) -> UITableViewCell // newer dequeue method guarantees a cell is returned and resized properly, assuming identifier is registered
 
 
 
dequeueReusableCellWithIdentifier(identifier: String, forIndexPath indexPath: NSIndexPath) guarantees you a cell..
 
 
Maybe these links are helpful :- 
 
Fatal error: unexpectedly found nil while unwrapping an Optional values
 
https://stackoverflow.com/a/25569704/6297658