ios - 仅当来自服务器的数据快速加载到第一个 View Controller 的核心数据中时，如何运行第二个 View Controller

Question

在我的应用程序中，当登录完成时，相同的 VC 数据从服务器加载到 coredata 中，但是在第二个 VC 的下一个 TableView 中将数据从服务器加载到 coredata 时延迟有空列表。所以，我只想在从第一个 VC 加载数据到 coredata 后运行第二个 vc。

for teEmp in json {

                    if teEmp.valueForKey("department") !== null {
                        if teEmp.valueForKey("department")  as! String == "Technology"{

                            // start core data

                            let entityDescription = NSEntityDescription.entityForName("Tech", inManagedObjectContext: self.managedObjectcontext!)
                            let tech = Employees(entity: entityDescription!,insertIntoManagedObjectContext: self.managedObjectcontext)

                            tech.id = teEmp.valueForKey("id")! as? String
                            tech.first_name = teEmp.valueForKey("firstname")! as? String
                            tech.card_id = (teEmp.valueForKey("cardId")!) as? String
                            tech.image = (teEmp.valueForKey("image")!) as? String
                            tech.last_name = (teEmp.valueForKey("lastname")!) as? String
                            tech.designation = (teEmp.valueForKey("designation")!) as? String
                            tech.department = (teEmp.valueForKey("department")!) as? String
                            if teEmp.valueForKey("startedDate") as! String != "null" {
                                let dateAsString = teEmp.valueForKey("startedDate")
                                dateFormatter.dateFormat = "MM/dd/YYYY"
                                let teStartDate = dateFormatter.dateFromString((dateAsString as? String)!)
                                dateFormatter.dateStyle = NSDateFormatterStyle.LongStyle
                                //dateFormatter.dateFormat = "MMM dd YYYY"
                                let techStartDay = dateFormatter.stringFromDate(teStartDate!)
                                tech.started_date = techStartDay as String
                            }
                            tech.departure_date = (teEmp.valueForKey("departureDate")!) as? String
                            tech.responsibilities = (teEmp.valueForKey("responsibilities")!) as? String
                            tech.address = (teEmp.valueForKey("address")!) as? String
                            tech.email = (teEmp.valueForKey("email")!) as? String
                            tech.shift = (teEmp.valueForKey("shift")!) as? String
                            tech.linkedIn_profile = (teEmp.valueForKey("linkedInProfile")!) as? String
                            tech.new_employee = (teEmp.valueForKey("newEmployee")!) as? String
                            tech.departed = (teEmp.valueForKey("departed")!) as? String
                            tech.supervisor = (teEmp.valueForKey("supervisor")!) as? String

                            if teEmp.valueForKey("birthDate") as! String != "null" {
                                let dateAsString = teEmp.valueForKey("birthDate")
                                dateFormatter.dateFormat = "MM/dd"
                                let teBirthDate = dateFormatter.dateFromString(dateAsString as! String)
                                dateFormatter.dateFormat = "MMM dd"
                                let techBirthMonth = dateFormatter.stringFromDate(teBirthDate!)
                                tech.birth_date = techBirthMonth
                            }

                            tech.privacy = (teEmp.valueForKey("privacy")!) as? String
                            if (teEmp.valueForKey("privacy")!) as? String == "PUBLIC"{
                                tech.contact = (teEmp.valueForKey("contact")!) as? String
                            } else {
                                tech.contact = "98********"
                            }



                            do {
                                try self.managedObjectcontext!.save()
                                print("Tech data saved in core data")

                            } catch let error as NSError
                            {
                                print(error.localizedDescription)


                            }
                            // end core data

                        }

                    }

                }

            }

        }catch  let error as NSError {
            print(error)
        }

        if(err != nil) {
            print(err!.localizedDescription)
            let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
            print("Error could not parse JSON: '\(jsonStr)'")

        }
        else {


        }

Answer 1

您可以使用 NSNotificationCenter/委托(delegate)模式/传递闭包/ReactiveCocoa 来实现这一点。这是一个使用 NSNotificationCenter 的例子。

do {
     try self.managedObjectcontext!.save()
     print("Tech data saved in core data")
     // Add this line
     let notificationCenter = NSNotificationCenter.defaultCenter()
     notificationCenter.postNotificationName("CoreDataSaved", object: nil)
}

然后转到您的 FirstViewController:在viewdidload方法中，添加如下-

let notificationCenter = NSNotificationCenter.defaultCenter()
notificationCenter.addObserver(self,
                   selector: "ShowSecondVC",
                   name:"CoreDataSaved",
                   object: nil
                    )

并添加推送第二个 View Controller 的功能。

func ShowSecondVC() {
  // Show second VC
}

最后，在 deinit block 中从 First VC 中删除通知监听器。

deinit {
  NSNotificationCenter.defaultCenter().removeObserver(self)
}