Swift：将 CoreData 获取为数组

Question

我想获取 sqlite 表中所有保存的数据。

我目前正在这样做：

 func GetAllData() -> NSArray
{
    var error : NSError? = nil;
    var request : NSFetchRequest = NSFetchRequest(entityName: "Locations");
    let result : [AnyObject] = managedObjectContext!.executeFetchRequest(request, error:&error)!;
      var elements : NSMutableArray = NSMutableArray();
    for fetchedObject in result
    {
        elements.addObject(fetchedObject[0]);
    }
    print(elements);
    return elements;
}

我在 Objective-C 中获取数据没有问题，但在 swift 中我不明白！

数据的保存工作正常。我有两行“名称”和“类别”。如何显示所有保存的数据？

Answer 1

您应该将所有对象从 CoreData 加载到 NSManaged 对象的数组/字典中。

例如：

    var locations  = [Locations]() // Where Locations = your NSManaged Class

    var fetchRequest = NSFetchRequest(entityName: "Locations")
    locations = context.executeFetchRequest(fetchRequest, error: nil) as [Locations]

    // Then you can use your properties.

    for location in locations {

      print(location.name)   

    }

Answer 2

试试这个：

let fetchRequest = NSFetchRequest(entityName: "Locations")
        
do {
     let results   = try managedObjectContext.executeFetchRequest(fetchRequest)
     let locations = results as! [Locations]
        
     for location in locations {
       print(location)   
     }

} catch let error as NSError {
  print("Could not fetch \(error)")
}

Answer 3

斯威夫特 3

func fetchData(){

    onlyDateArr.removeAll()
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "PhotoData")

    do {
        let results = try context.fetch(fetchRequest)
        let  dateCreated = results as! [PhotoData]

        for _datecreated in dateCreated {
            print(_datecreated.dateCreation!)
            onlyDateArr.append(_datecreated)
        }
    }catch let err as NSError {
        print(err.debugDescription)
    }


}

Answer 4

2020 语法

复制粘贴

func grabAllPersons() {
    var pp: [CD_Person] = []
    do {
        let r = NSFetchRequest<NSFetchRequestResult>(entityName: "CD_Person")
        let f = try core.container.viewContext.fetch(r)
        pp = f as! [CD_Person]
    } catch let error as NSError {
        print("woe grabAllPersons \(error)")
    }
    
    for p: CD_Person in pp {
        print(" >> \(p.firstName)")
    }
}

请注意，core.container.viewContext 是“您的”上下文，通常（但不总是）由core.container.viewContext 提供。 (Example)

关键提示...

在某些情况下：

请务必绝对不要意外使用“错误”上下文。

例如，您正在做一件小事，例如数数或只是抓住所有物品。

这个问题在HERE的大标题下解释了“exerexextreme care...”

Answer 5

您不必（强制）从 NSFetchRequest 转换任何结果：

var locations  = [Locations]()
var fetchRequest = NSFetchRequest<Locations>(entityName: "Locations") //Note the <Locations> makes the NSFetchRequestResult to an array of Locations 
locations = context.executeFetchRequest(fetchRequest, error: nil)
 
for location in locations {
    print(location.name)   
}

---

另一个注意事项：通常您应该以单数形式命名实体，例如“Location”，而不是“Locations”。然后位置数组是位置。 let locations = Array<Location>(location1, location2)

Answer 6

import UIKit
import CoreData
class CoreDataHandler: NSObject {

    private class func getContext() -> NSManagedObjectContext
    {
        let delegate = UIApplication.shared.delegate as? AppDelegate

        return (delegate?.persistentContainer.viewContext)!
    }


    class func saveObeject (name:String,roll:String,college:String)
    {
        let context =  getContext()
        let entity = NSEntityDescription.entity(forEntityName: "CountryInfo", in: context)

        let manageObjet = NSManagedObject(entity: entity!, insertInto: context)

        manageObjet.setValue(name, forKey: "name")
        manageObjet.setValue(roll, forKey: "roll")
        manageObjet.setValue(college, forKey: "college")


        do
        {
            try context.save()
        }catch
        {
            print("unable to save data")
        }
    }

    class func getCountryDetail(name:String) ->Array<Any>?
    {

        // return "http://1.bp.blogspot.com/-J9emWhBZ_OM/TtQgVQmBHRI/AAAAAAAAD2w/j7JJMRMiuAU/s1600/Al_Ain_FC.png"
        let contecxt = getContext()
        let fetchRequest:NSFetchRequest<CountryInfo> = CountryInfo.fetchRequest()

        var user:[CountryInfo] = []
        let predicate = NSPredicate(format: "name LIKE[cd] %@",name)
        fetchRequest.predicate = predicate
        do{
            user =  try contecxt.fetch(fetchRequest)
            let ClubInfoBO = user
            print(ClubInfoBO)
            return (ClubInfoBO) as? Array<Any>
        }catch
        {
            return nil

        }

    }


    class func deleteObject(user:CountryInfo) ->Bool{
        let context = getContext()
        context.delete(user)
        do
        {
            try context.save()
            return true
        }catch{
            return false
        }
    }

    //Clean delete

    class func cleanDelete () ->Bool
    {
        let context = getContext()
        let delete = NSBatchDeleteRequest(fetchRequest: CountryInfo.fetchRequest())

        do{
            try context.execute(delete)
            return true
        }catch
        {
            return false
        }
    }
}