swift
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swift [2023/11/19 22:13] admin |
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| [[https://developer.apple.com/library/archive/documentation/General/Conceptual/iCloudDesignGuide/Chapters/DesigningForKey-ValueDataIniCloud.html#//apple_ref/doc/uid/TP40012094-CH7|Apple: Designing for Key-Value Data in iCloud]] | [[https://developer.apple.com/library/archive/documentation/General/Conceptual/iCloudDesignGuide/Chapters/DesigningForKey-ValueDataIniCloud.html#//apple_ref/doc/uid/TP40012094-CH7|Apple: Designing for Key-Value Data in iCloud]] | ||
| - | ### Relationship Between Entities in CoreData | + | ### Relationship: Connect entities in CoreData |
| ref: https://www.hackingwithswift.com/books/ios-swiftui/one-to-many-relationships-with-core-data-swiftui-and-fetchrequest | ref: https://www.hackingwithswift.com/books/ios-swiftui/one-to-many-relationships-with-core-data-swiftui-and-fetchrequest | ||
| - | Step by Step: | ||
| 1. Create Entities in CoreData | 1. Create Entities in CoreData | ||
| Line 87: | Line 86: | ||
| 5. In `...CoreDataProperties` file, you should be able to see code like below for adding transactions to this certain piggy object. | 5. In `...CoreDataProperties` file, you should be able to see code like below for adding transactions to this certain piggy object. | ||
| - | ```swift | + | ``` |
| extension Piggy { | extension Piggy { | ||
| Line 121: | Line 120: | ||
| 2. In ` ...CoreDataProperties` file, `transactions` is an `NSSet`, perform the following steps to convert it from an `NSSet` to a `Set<PurchasedItem>` – a Swift-native type where the types of its contents is specificy to `PurchasedItem` type. Convert that `Set<PurchasedItem>` into an array, so that `ForEach` can read individual values from there. Sort that array, so the transactions come in a sensible order. | 2. In ` ...CoreDataProperties` file, `transactions` is an `NSSet`, perform the following steps to convert it from an `NSSet` to a `Set<PurchasedItem>` – a Swift-native type where the types of its contents is specificy to `PurchasedItem` type. Convert that `Set<PurchasedItem>` into an array, so that `ForEach` can read individual values from there. Sort that array, so the transactions come in a sensible order. | ||
| - | ```swift | + | ``` |
| public var transactionArray: [PurchasedItem] { | public var transactionArray: [PurchasedItem] { | ||
| let set = transactions as? Set<PurchasedItem> ?? [] | let set = transactions as? Set<PurchasedItem> ?? [] | ||
| Line 133: | Line 132: | ||
| 1. Use them in your View: To read purchased items connected to a certain piggy in a View. Use the following code: | 1. Use them in your View: To read purchased items connected to a certain piggy in a View. Use the following code: | ||
| - | ```swift | + | ``` |
| struct HistoryView: View { | struct HistoryView: View { | ||
| @Environment(\.managedObjectContext) private var viewContext | @Environment(\.managedObjectContext) private var viewContext | ||
| Line 165: | Line 164: | ||
| Or use the following code. However with this method the HistoryView won't update if you add new purchasedItem (transaction) because it is only monitoring the object `piggy`. To trigger view update when purchasedItem is added, you need to use the method above to fetch `PurchasedItem` directly. | Or use the following code. However with this method the HistoryView won't update if you add new purchasedItem (transaction) because it is only monitoring the object `piggy`. To trigger view update when purchasedItem is added, you need to use the method above to fetch `PurchasedItem` directly. | ||
| - | ```swift | + | ``` |
| struct HistoryView: View { | struct HistoryView: View { | ||
| @Environment(\.managedObjectContext) private var viewContext | @Environment(\.managedObjectContext) private var viewContext | ||
swift.1700403186.txt.gz · Last modified: 2023/11/19 22:13 by admin