do语句

Question

比方说，这是我们从模型中删除对象功能：

func delete(indexPath: IndexPath) { 

    let managedObject = self.fetchedResultsController.object(at: indexPath) 
    self.managedObjectContext.delete(managedObject) 

    do { 

     // Save changes 
     try self.managedObjectContext.save() 

     // Cancel the notification 
     let center = UNUserNotificationCenter.current() 
     center.removeDeliveredNotifications(withIdentifiers: [managedObject.uuid!]) 
     center.removePendingNotificationRequests(withIdentifiers: [managedObject.uuid!]) 

     // Reload tableView 
     self.tableView.reloadData() 

    } catch { 

     let alertController = UIAlertController.init(title: "Error", message: "We are sorry! Unknown error occured...", preferredStyle: .alert) 
     alertController.addAction(UIAlertAction.init(title: "Close", style: .default, handler: { (action) in 
      // Completion handler 
     })) 
     self.present(alertController, animated: true, completion: { 
      // Completion block 
     }) 
    } 
} 

问：

如果错误抛出，执行转移到catch条款。这很好。但是这些语句会发生什么（其余的代码，取消通知和重新加载tableView）？那些语句仍然可执行或简单地被忽略？

Answer 1

如果您希望即使发生错误仍然调用您的代码，您可以为其创建单独的函数，并从do和catch语句的末尾调用它。或者您可以将该代码放在defer声明中。

要么像

func delete(indexPath: IndexPath) { 

let managedObject = self.fetchedResultsController.object(at: indexPath) 
self.managedObjectContext.delete(managedObject) 

do { 

    // Save changes 
    try self.managedObjectContext.save() 
    reloadCode() 

} catch { 
    reloadCode() 
    let alertController = UIAlertController.init(title: "Error", message: "We are sorry! Unknown error occured...", preferredStyle: .alert) 
    alertController.addAction(UIAlertAction.init(title: "Close", style: .default, handler: { (action) in 
     // Completion handler 
    })) 
    self.present(alertController, animated: true, completion: { 
     // Completion block 
    }) 
} 
} 

func reloadCode() { 
     // Cancel the notification 
     let center = UNUserNotificationCenter.current() 
     center.removeDeliveredNotifications(withIdentifiers: [managedObject.uuid!]) 
     center.removePendingNotificationRequests(withIdentifiers: [managedObject.uuid!]) 

     // Reload tableView 
     self.tableView.reloadData() 

} 

或者更整齐，

FUNC删除（indexPath：IndexPath）{

let managedObject = self.fetchedResultsController.object(at: indexPath) 
self.managedObjectContext.delete(managedObject) 


    defer { 
let center = UNUserNotificationCenter.current() 
     center.removeDeliveredNotifications(withIdentifiers: [managedObject.uuid!]) 
     center.removePendingNotificationRequests(withIdentifiers: [managedObject.uuid!]) 

     // Reload tableView 
     self.tableView.reloadData() 
} 
do { 

    // Save changes 
    try self.managedObjectContext.save() 

    // Cancel the notification 


} catch { 

    let alertController = UIAlertController.init(title: "Error", message: "We are sorry! Unknown error occured...", preferredStyle: .alert) 
    alertController.addAction(UIAlertAction.init(title: "Close", style: .default, handler: { (action) in 
     // Completion handler 
    })) 
    self.present(alertController, animated: true, completion: { 
     // Completion block 
    }) 
} 

}