Swift CoreData 基础向

创建项目使用coredata模版

框架创建

lifetrip.xcdatamodeld
Persistence.swift

使用

lifetrip.xcdatamodeld 添加实体

添加实体


1. coredata保存与查询

   代理注入环境

   ContentView()
       .environment(\.managedObjectContext, PersistenceController.shared.container.viewContext)

初始化查询

@Environment(\.managedObjectContext) private var viewContext
    
@FetchRequest(
    sortDescriptors: [NSSortDescriptor(keyPath: \FootmarkEntity.startTime, ascending: false)],
    animation: .default)
private var footmarks: FetchedResults<FootmarkEntity>

保存（新增）viewContext.save()

private func addItem() {
    withAnimation {
        let newItem = FootmarkEntity(context: viewContext)
        // 实体赋值
        let randomNumber:Int = Int(arc4random() % 100) + 1
        newItem.id  = String(randomNumber);
        newItem.endTime = Date()
        newItem.startTime = Date()
        // 保存
        do {
            try viewContext.save()
        } catch {
            let nsError = error as NSError
            fatalError("添加失败 \(nsError), \(nsError.userInfo)")
        }
    }
}

2. 预览模式

   代码

   struct LabelView_Previews: PreviewProvider {
       static var previews: some View {
           let labelEntity: LabelEntity = { () -> LabelEntity in
               let labelEntity = LabelEntity(context: PersistenceController.preview.container.viewContext)
               labelEntity.picture = UIImage(named: "nekosensei")!.pngData()
               return labelEntity
           }()
           return LabelCardView(labelEntity: labelEntity)
       }
   }