比较 Fetchrequest Xcode Swift OSX 核心数据的谓词中的 NSSet

Posted 2023-03-04

【中文标题】比较 Fetchrequest Xcode Swift OSX 核心数据的谓词中的 NSSet

【英文标题】：compare NSSet in Predicate for Fetchrequest Xcode Swift OSX Core Data

【发布时间】：2016-08-11 09:26:02

【问题描述】：

我有两个NSManagedObject 喜欢

class Person: NSManagedObject 

    @NSManaged var firstname: String;
    @NSManaged var lastname: String;
    @NSManaged var code: String;
    @NSManaged var position: Int16;
    @NSManaged var lasttime: NSDate;
    @NSManaged var isvip: Int16;    
    @NSManaged var changeposition: NSSet;   



class ChangePosition: NSManagedObject 

    @NSManaged var person:Person
    @NSManaged var code: String;
    @NSManaged var from: Int16;
    @NSManaged var to: Int16;
    @NSManaged var time: NSDate;   

所以我有一个人与许多ChangePosition 作为NSSet。每个ChangePosition 都有一个NSDate。

现在我想尝试从NSDate 最高的人那里获取ChangePosition。我可以为此使用哪个谓词结构？

【参考方案1】：

所以我的实际工作流程就是这个

let fetchReqPerson = NSFetchRequest(entityName: "Person");
        //fetchReq.predicate = NSPredicate(format: "ANY personchangeposition.time == maxElement(personchangeposition.time)")



        do 

            let fetchResult = try self.appDelegate.managedObjectContext.executeFetchRequest(fetchReqPerson)

            for managedObject in fetchResult 

                var bigTime:PersonChangePosition?


                for changes in (managedObject as! Person).personchangeposition 



                    if (changes as! PersonChangePosition).time.compare(_date) == NSComparisonResult.OrderedAscending 

                        if bigTime == nil 
                            bigTime = changes as! PersonChangePosition
                         else 

                            if (changes as! PersonChangePosition).time.compare(bigTime!.time) == NSComparisonResult.OrderedDescending 
                                bigTime = changes as! PersonChangePosition;
                            

                        

                    

                

                if bigTime != nil 
                    //print("bigTime: ",bigTime!.time, "to: ",bigTime!.to)

                    self.fetchResultPerson.append(bigTime!)
                



            


            self.fetchForRecord = self.fetchResultPerson;

            //print("fetchResult fetchResultPerson: ",fetchResultPerson.count)


             catch let fetchError as NSError 

            print("Fetching error: ",fetchError)
            



            //

            switch(self.areaSegementControl.selectedSegment)


            case 0: self.fetchForRecord = try self.fetchForRecord.filter($0.to != 4)
            break;

            case 1: self.fetchForRecord = try self.fetchForRecord.filter($0.to == 1 || $0.to == 3)
            break;

            case 2: self.fetchForRecord = try self.fetchForRecord.filter($0.to == 2)
            break;

            default:
            break;

            

当然，它相当慢......不是很好