如何从coredata中的实体中获取过滤后的数据

Question

我有一个场景，我知道我需要做什么，但不知道如何在 Swift...

中实现它

我在 CoreData 中有 2 个 table，我获取它们的值如下

我需要的 - 特定用户朋友数组中的所有朋友

//-----完整代码手动缓存用户 Class

import Foundation
import CoreData


extension CachedUser {

@nonobjc public class func fetchRequest() -> NSFetchRequest<CachedUser> {
    return NSFetchRequest<CachedUser>(entityName: "CachedUser")
}

@NSManaged public var name: String?
@NSManaged public var id: String?
@NSManaged public var company: String?
@NSManaged public var isActive: Bool
@NSManaged public var age: Int16
@NSManaged public var email: String?
@NSManaged public var address: String?
@NSManaged public var about: String?
@NSManaged public var registered: String?
@NSManaged public var tags: String?
@NSManaged public var friends: NSSet?

public var wrappedName: String {
    name ?? "Name N/A"
}

public var wrappedId: String {
    id ?? "id N/A"
}

public var wrappedCompany: String {
    company ?? "comapny N/A"
}

public var wrappedIsActive: Bool {
    isActive
}


public var checkIsActive: String {
    return isActive ? "YES" :"NO"
}

public var wrappedEmail: String {
    email ?? "email N/A"
}

public var wrappedAge: Int16 {
    age
}

public var wrappedRegistered: String {
    registered ?? "N/A"
}



public var cachedFriend: [CachedFriend] {
    let set = friends as? Set<CachedFriend> ?? []
    return set.sorted {
        [=10=].wrappedName < .wrappedName
    }
}

}

// MARK：为朋友生成的访问器扩展 CachedUser {

@objc(addFriendsObject:)
@NSManaged public func addToFriends(_ value: CachedFriend)

@objc(removeFriendsObject:)
@NSManaged public func removeFromFriends(_ value: CachedFriend)

@objc(addFriends:)
@NSManaged public func addToFriends(_ values: NSSet)

@objc(removeFriends:)
@NSManaged public func removeFromFriends(_ values: NSSet)

}

extension CachedUser : Identifiable {

}

//-----

//----- CachedUSer

import Foundation
import CoreData


extension CachedFriend {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<CachedFriend> {
        return NSFetchRequest<CachedFriend>(entityName: "CachedFriend")
    }

    @NSManaged public var name: String?
    @NSManaged public var id: String?
    @NSManaged public var users: CachedUser?
    
    
    public var wrappedId: String {
        id ?? "Unknown Id"
    }
    
    public var wrappedName: String {
        name ?? "Unknown Name"
    }
    

}

extension CachedFriend : Identifiable {

}

//------

//---SwiftUI查看我要的数据，版块好友不显示任何好友

import SwiftUI

struct DetailView: View {
    let users: [CachedUser]
    let user: CachedUser
    @State var friendsArray: [CachedFriend] = []
    @FetchRequest(sortDescriptors: []) var friendsData: FetchedResults<CachedFriend>
    var body: some View {
        Form {
            List {
                Section("Name") {
                    Text(user.wrappedName)
                        .font(.body)
                }
                Section("email") {
                    Text(user.wrappedEmail)
                }
                Section("Registration Date") {
                    Text(user.wrappedRegistered)
                }
                Section("Company") {
                    Text(user.wrappedCompany)
                }
                Section("Is Active") {
                    Image(systemName: user.isActive ? "checkmark.circle.fill" : "xmark.octagon.fill")
                        .foregroundColor(user.isActive ? Color.green : Color.red)
                }
                
                Section("Friends") {
                    List {
                  
                        ForEach(friendsArray, id:\.self) {friend in
                        Text(friend.wrappedName)
                    }
                        
                    }
                  
                    
                }
                
               
                               
                
            }
            .onAppear {
                friendsArray = Array(user.cachedFriend)
            }
           
           
            
           
            }
           
          
        }
        
   
    
  
}

//-----结束这里我有一个 CachedUser 实体和 CachedFriend 实体关系图像。

每个用户都有我从 json 文件中获得的朋友数组，该朋友数组包含姓名和 ID....

我知道我必须遍历朋友 table 并过滤所有与用户朋友数组中名称相同的名称，但我似乎做不到，我在下面尝试过，但他们只是不工作，任何人都可以指出我正确的方向。谢谢

  @State var friendsArray: [CachedFriend] = []
 let user: CachedUser
func findFriend()  {
    for allFriend in friendsData {
           
        friendsArray = user.cachedFriend.filter({ item in
            item.wrappedId == allFriend.wrappedId
        })
           
    }
    
    print(friendsArray.count)
}

json

样本

[
    {
        "id": "50a48fa3-2c0f-4397-ac50-64da464f9954",
        "isActive": false,
        "name": "Alford Rodriguez",
        "age": 21,
        "company": "Imkan",
        "email": "alfordrodriguez@imkan.com",
        "address": "907 Nelson Street, Cotopaxi, South Dakota, 5913",
        "about": "Occaecat consequat elit aliquip magna laboris dolore laboris sunt officia adipisicing reprehenderit sunt. Do in proident consectetur labore. Laboris pariatur quis incididunt nostrud labore ad cillum veniam ipsum ullamco. Dolore laborum commodo veniam nisi. Eu ullamco cillum ex nostrud fugiat eu consequat enim cupidatat. Non incididunt fugiat cupidatat reprehenderit nostrud eiusmod eu sit minim do amet qui cupidatat. Elit aliquip nisi ea veniam proident dolore exercitation irure est deserunt.",
        "registered": "2015-11-10T01:47:18-00:00",
        "tags": [
            "cillum",
            "consequat",
            "deserunt",
            "nostrud",
            "eiusmod",
            "minim",
            "tempor"
        ],
        "friends": [
            {
                "id": "91b5be3d-9a19-4ac2-b2ce-89cc41884ed0",
                "name": "Hawkins Patel"
            },
            {
                "id": "0c395a95-57e2-4d53-b4f6-9b9e46a32cf6",
                "name": "Jewel Sexton"
            },
            {
                "id": "be5918a3-8dc2-4f77-947c-7d02f69a58fe",
                "name": "Berger Robertson"
            },
            {
                "id": "f2f86852-8f2d-46d3-9de5-5bed1af9e4d6",
                "name": "Hess Ford"
            },
            {
                "id": "6ba32d1b-38d7-4b0f-ba33-1275345eacc0",
                "name": "Bonita White"
            },
            {
                "id": "4b9bf1e5-abec-4ee3-8135-3a838df90cef",
                "name": "Sheryl Robinson"
            },
            {
                "id": "5890bacd-f49c-4ea2-b8fa-02db0e083238",
                "name": "Karin Collins"
            },
            {
                "id": "29e0f9ee-71f2-4043-ad36-9d2d6789b2c8",
                "name": "Pace English"
            },
            {
                "id": "aa1f8001-59a3-4b3c-bf5e-4a7e1d8563f2",
                "name": "Pauline Dawson"
            },
            {
                "id": "d09ffb09-8adc-48e1-a532-b99ae72473d4",
                "name": "Russo Carlson"
            },
            {
                "id": "7ef1899e-96e4-4a76-8047-0e49f35d2b2c",
                "name": "Josefina Rivas"
            }
        ]
    },

Answer 1

您永远不需要在 CoreData FetchRequest 上使用 filter。

最好按NSPredicate

过滤

https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/CoreData/index.html

但在这种情况下，用户的所有好友都在一个变量中。如果你有个人 user 你需要做的就是这样......

user.friends.allObjects

如何从coredata中的实体中获取过滤后的数据

How to get filtered data from entities in coredata

core-data

swiftui