CoreData的使用（二）---增删改查

CoreData是苹果自带的一种持久化数据存储的方式，网上很多人说使用起来麻烦，其实正真使用后发现还是蛮方便的，又是系统自带的，其实我还是蛮推荐使用的

• 添加数据操作

func addDemo() {
        
        let entity: NSEntityDescription = NSEntityDescription.entity(forEntityName: "DemoModel", in: CONTEXT)!
        let model = DemoModel(entity: entity, insertInto: CONTEXT)
        
        model.id = "1"
        model.title = "数据模型添加数据"
        
        do {
            try CONTEXT.save()
        }catch {
            print("添加数据失败:\(error.localizedDescription)")
        }
    }

• 删除数据

func deleteDemo() {
        
        let request: NSFetchRequest<DemoModel> = DemoModel.fetchRequest()
        
        do {
            let array = try CONTEXT.fetch(request)
            for model in array {
                CONTEXT.delete(model)
            }
            try CONTEXT.save()
        }catch {
            print("删除数据失败\(error.localizedDescription)")
        }
    }

• 查询数据

func findDemo() {
        
        let request: NSFetchRequest<DemoModel> = DemoModel.fetchRequest()
        //条件查询：id==1的数据
        let predicate: NSPredicate = NSPredicate(format: "id = %@", "1")
        request.predicate = predicate
        //排序：根据id来排序
        let sort: NSSortDescriptor = NSSortDescriptor(key: "id", ascending: false)
        request.sortDescriptors = [sort]
        
        do {
            //查询的结果：是个数组
            let array = try CONTEXT.fetch(request)
        }catch {
            print("查询数据失败\(error.localizedDescription)")
        }
    }

• 更新数据

func updateDemo() {
        
        let request: NSFetchRequest<DemoModel> = DemoModel.fetchRequest()
        //条件查询：id==1的数据
        let predicate: NSPredicate = NSPredicate(format: "id = %@", "1")
        request.predicate = predicate
        //排序：根据id来排序
        let sort: NSSortDescriptor = NSSortDescriptor(key: "id", ascending: false)
        request.sortDescriptors = [sort]
        
        do {
            //查询的结果：是个数组
            let array = try CONTEXT.fetch(request)
            for model in array {
                model.title = "更新数据"
            }
            try CONTEXT.save()
        }catch {
            print("更新数据失败\(error.localizedDescription)")
        }
    }

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