Mic*_*ito 8 core-data ios swift3 xcode8
我查看了Apple的:
Xcode 8发行说明:https:
//developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Introduction.html
从Swift 2.2迁移到Swift 2.3或Swift 3
https://swift.org/migration-guide/
在macOS 10.12,iOS 10.0,tvOS 10.0和watchOS 3.0中的核心数据有什么新功能
https://developer.apple.com/library/content/releasenotes/General/WhatNewCoreData2016/ReleaseNotes.html#//apple_ref/doc/uid/ TP40017342-CH1-DontLinkElementID_1
还有很多其他......但是,应该从Apple的核心数据编程指南中获得的一个文档尚未从Swift 2更新
.https://developer.apple.com/library/content/documentation/Cocoa/概念/ CoreData/FetchingObjects.html#// apple_ref/DOC/UID/TP40001075-CH6-SW1
理想情况下,我正在寻找类似这样的东西,但对于Swift 3.
https://www.raywenderlich.com/115695/getting-started-with-core-data-tutorial
任何线索都会非常感激.
每个汤姆的评论(下面)我错过了什么步骤？
1)创建一个新项目"测试"
2)选择使用CoreDate(这会创建Test.xcdatamodeld)
这将使用以下内容自动填充AppDelegate(删除默认注释):
func applicationWillTerminate(_ application: UIApplication) {
self.saveContext()
}
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "Test")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
3)创建实体"Foo"
4)添加属性"bar"类型String
5)在ViewController.swift下添加以下内容(这是从Apple复制的,我只是将"... use"替换为"print")
func findAnimals() {
let request: NSFetchRequest<Foo> = Foo.fetchRequest
do {
let searchResults = try context.fetch(request)
print(searchResults)
} catch {
print("Error with request: \(error)")
}
}
6)在override func viewDidLoad()下添加findAnimals().
但是这有错误:
7)所以你回去此的viewController下添加了一些功能,使访问的容器(这是不是在本例中形成苹果).
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext很好,我们清除了2错误中的1,但错误"使用未声明的类型'NSFetchRequest'"仍然存在.
这就是我被困住的地方.即使在审查了所有Apple发布的材料后,我也找不到完整的例子.
@Aaron再次感谢视频链接,让我走上正轨.下面是使用Xcode 8中的Swift 3从核心数据中获取,添加和清除所需的最低限度.
在Class ViewController下添加以下内容:
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
// Get data from he attribute
func getSample() {
let request: NSFetchRequest = SampleEntity.fetchRequest()
request.resultType = NSFetchRequestResultType.dictionaryResultType
do {
let searchResults = try context.fetch(request as! NSFetchRequest<NSFetchRequestResult>) as! [NSDictionary]
let searchResultsArray = searchResults.map { $0["sampleAttribute"] as! String}
print("searchResultsArray", searchResultsArray)
} catch {
print("Error with request: \(error)")
}
}
// Save to the attribute
func setSample() {
let saveSample = SampleEntity(context: context)
saveSample.sampleAttribute = "Save a new string."
do {
try context.save()
} catch {
print("Error with save: \(error)")
}
}
// clear the attribute
func resetSample() {
let clearSample: NSFetchRequest = SampleEntity.fetchRequest()
let deleteResults = NSBatchDeleteRequest(fetchRequest: clearSample as! NSFetchRequest<NSFetchRequestResult>)
do {
try context.execute(deleteResults)
try context.save()
} catch {
print("Error with save: \(error)")
}
}在override func viewDidLoad()下添加以下内容:
getSample() setSample() getSample() resetSample() getSample()
运行,您将在调试区域中看到以下内容:
searchResultsArray [] // Initially the attribute is empty searchResultsArray ["Save new string."] // The attribute now contains the string searchResultsArray [] // This attribute has been cleared
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