【Swift学习笔记-《PRODUCT》读书记录-CoreData数据存储】

《PRODUCT》中小记记录的文字信息，都是使用CoreData存储在本地的。下面将详细介绍，如何在xcode8中使用CoreData。

首先新建一个数据模型文件Diary.Xcatamodeld文件，如图：



选中这个数据库文件，右边可以给这个表增加属性字段



完成后，选中该文件，点击Editor菜单中的，“Ctreate NSManageObject Subclass”导出生成NSManagedObject



然后再对数据库文件做初始化，在appdelegate中创建managedObjectModel

lazy var managedObjectModel: NSManagedObjectModel = {
// 描述数据模型描述文件存储位置
let modelURL = Bundle.main.url(forResource: "DiaryText", withExtension: "momd")!
return NSManagedObjectModel(contentsOf: modelURL)!
}()

创建persitentStoreCoordinator持久化管理

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
// 通过 managedObjectModel 创建持久化管理
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel:self.managedObjectModel)

let url = self.applicationDocumentsDirectory.appendingPathComponent("DiaryText2.sqlite")
// 设定数据库存储位置

var error: NSError? = nil
var failureReason = "载入程序存储的数据出错."

do {
try coordinator!.addPersistentStore(
ofType: NSSQLiteStoreType, configurationName: nil,
at: url, options: nil)
// 创建NSSQLiteStoreType类型持久化存储
} catch var error1 as NSError {
error = error1
coordinator = nil
// 报告错误
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "无法初始化程序存储的数据" as AnyObject?
dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?
dict[NSUnderlyingErrorKey] = error
error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
NSLog("发现错误 \(error), \(error!.userInfo)")
abort()
} catch {
fatalError()
}

return coordinator
}()

创建managedObjectContext数据库上下文：

lazy var managedObjectContext: NSManagedObjectContext? = {
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()

因为后续会项目中会时常使用上下文，所以在appdelegate中定义了一个常量

// Coredata
let appDelegate = UIApplication.shared.delegate as! AppDelegate

let managedContext = appDelegate.managedObjectContext!

到这里数据库基本初始化完成。接下来就是保存数据了，点击完成按钮保存数据

func ednBtnClick() { // 保存数据
self.titleView.endEditing(true)
self.contentView.endEditing(true)
if contentView.text.lengthOfBytes(using: String.Encoding.utf8) > 0 {
let entity =  NSEntityDescription.entity(forEntityName: "DiaryText", in: managedContext)

let newdiary = DiaryText(entity: entity!,
insertInto:managedContext)
newdiary.context = contentView.text
newdiary.location = "123"
if titleView.text.lengthOfBytes(using: String.Encoding.utf8) > 0 {
newdiary.title = titleView.text
}
var error:NSError?
do{
try managedContext.save()

}catch let error1 as NSError{
error = error1
print("保存出错\(error),\(error?.userInfo)")
}

}

self.navigationController?.popToRootViewController(animated: true)
}

还可以自行在diary数据库文件中扩展方法。

接下来介绍怎么从CoreData中查询想要的信息。

// 查询数据

do {
// 新建查询
let fetchRequest = NSFetchRequest<DiaryText>(entityName:"DiaryText")

// 排序方式
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "created_at", ascending: true)]

// 排序方式
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "context", ascending: true)]

fetched = NSFetchedResultsController(fetchRequest: fetchRequest,
managedObjectContext: managedContext, sectionNameKeyPath: "year",
cacheName: nil)

// 建立委托关系
//            fetchedResultsController.delegate = self

// 尝试查询
try self.fetched.performFetch()

if (fetched.fetchedObjects!.count == 0){
print("没有存储结果")
}else{
if let sectionsCount = fetched.sections?.count {
yearsCount = sectionsCount
diartys = fetched.fetchedObjects!
}else{
yearsCount = 1
sectionsCount = 0
}

}

} catch let error as NSError {
NSLog("发现错误 \(error.localizedDescription)")
}
for obj in diartys{
print("\(obj.context),,,\(obj.title)")
//            managedContext.delete(obj)
}

}

以上便是CoreData使用介绍