如何从coredata中的实体获取过滤数据
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【中文标题】如何从coredata中的实体获取过滤数据【英文标题】：How to get filtered data from entities in coredata 【发布时间】：2021-12-24 15:28:04 【问题描述】：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 个表，我获取它们的值如下
我需要什么 - 特定用户好友数组中的所有好友
//-----完整代码 手动 CachedUser 类
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
$0.wrappedName < $1.wrappedName
// MARK：为好友生成的访问器 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
//-----
//-- 缓存用户
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查看我要数据的地方，部分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 在这里，我附上了一个 CachedUser 实体和 CachedFriend 实体的关系图像。
每个用户都有我从 json 文件中获得的朋友数组，该朋友数组包含名称和 id....
我知道我必须遍历朋友表并过滤与用户朋友数组中同名的所有名称，但我似乎无法做到这一点，我在下面尝试过，但它们不起作用，可以任何人都指向我正确的方向。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 示例
[
"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"
]
,
【问题讨论】：
你什么都不用做，一个用户的朋友就是属性user.friends。这是一个集合，所以你可能想做friendsArray = Array(user.friends)
谢谢，我试过了 - public var cachedFriend: [CachedFriend] let set = friends as?设置您永远不需要在 CoreData FetchRequest 上使用 filter。
最好用NSPredicate做过滤
https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/CoreData/index.html
但在这种情况下，用户的所有朋友都在一个变量中。如果你有个人user，你需要做的就是这样......
user.friends.allObjects
【讨论】：
谢谢，我已经用 cmets 更新了问题，在最上面显示了你的名字，因为我使用一种方式来转换朋友作为？ Set以上是关于如何从coredata中的实体获取过滤数据的主要内容，如果未能解决你的问题，请参考以下文章
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