Question

在我的应用中，我正在使用Core Data。现在我想从数据库中获取数据，为此我使用获取请求。但是我想在单个获取请求中使用两个NSPrediate，所以我该怎么做呢。

这是我的代码：

let feedfetch = NSFetchRequest(entityName: "Feed")
feedfetch.predicate = NSPredicate(format: "userid == %@", userid)

let fetchedPerson = try moc.executeFetchRequest(feedfetch)

但是我想使用两个或更多谓词，那么我该怎么做呢？

我想在一个获取请求中调用所有这些，所以我该怎么做

let feedfetch = NSFetchRequest(entityName: "Feed")
feedfetch.predicate = NSPredicate(format: "userid == %@", userid)
feedfetch.predicate = NSPredicate(format: "is_deleted == %@", "0")
let sortDescriptor = NSSortDescriptor(key: "feed_id", ascending: false,selector: #selector(NSString.localizedStandardCompare))
feedfetch.sortDescriptors = [sortDescriptor]

let fetchedPerson = try moc.executeFetchRequest(feedfetch)

Answer 1

如果您出于任何原因需要使用两个谓词（scale_fill_gradientn(colours = c("blue","white","red"), values = c(0,5,10), guide = "colorbar", limits=c(0,10))个对象）而不是一行：

NSPredicate

然后使用"(userid == %@) AND (is_deleted == %@)" API：

NSCompoundPredicate

Answer 2

获取和排序

    let appDel: AppDelegate = UIApplication.shared.delegate as! AppDelegate
    let context:NSManagedObjectContext = appDel.managedObjectContext

    //Getting the cards with a video from Core Data filtered by  ("save")  and be an empity string  ("")  and by ("All")
    //Fetching from DB Card
    let savedCardRequestForVideo:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Card")

    //Creating mulit variables for filtering
    //Creating a variable "save" for filtering Core Data
    let savedCardFilterForVideo    = "save"

    //Creating a variable with an empty string "" for filtering Core Data
    let cardSortingIDForVideo      = ""

    //Creating a variable "All" for filtering Core Data
    let savedCardFilterForVideoAll = "All"

    //Creating the predicate array
     savedCardRequestForVideo.predicate = NSCompoundPredicate(type:.and, subpredicates:[
        NSPredicate(format: "saveVideoControl = %@", savedCardFilterForVideo),
        NSPredicate(format: "cardSortingID = %@", cardSortingIDForVideo),
        NSPredicate(format: "allData == %@", savedCardFilterForVideoAll)])


    //Here we are sorting the reuslts in a ascending order
    let savedSortDescriptorForVideo                = NSSortDescriptor(key: "businessName", ascending: ascendingOrDescending)
        savedCardRequestForVideo.sortDescriptors   = [savedSortDescriptorForVideo]

    //Creating a variable to hold the results that are being fetched
    let savedCardFilterResultsFoeVideo             = try! context.fetch(savedCardRequestForVideo) as! [NSManagedObject]

    //The variable savedCardsForVideo will hold the results array
    savedCardsForVideo  = savedCardFilterResultsFoeVideo  //This ia an Array<AnyObject>

如何在单次获取请求中调用两个NSPredicate。核心数据iOS Swift

2 个答案: