ios – 使用Swift 3在Xcode 8中寻找关于修订的NSPersistentContainer的清晰教程

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)")
        }
    }
}

func findAnimals() {
    let request: NSFetchrequest<Foo> = Foo.fetchrequest
    do {
        let searchResults = try context.fetch(request)
        print(searchResults)
    } catch {
        print("Error with request: \(error)")
    }
}

let context = (UIApplication.shared.delegate as! AppDelegatE).persistentContainer.viewContext

@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的快速浏览.

>新项目> iOS单一视图应用程序
>产品名称：“样品”
>使用核心数据(已选中)
>保存
>打开Sample.xcdatamodeld
>添加和实体：“SampleEntity”
>使用数据模型检查器将Codegen(在Class下)设置为“Class DeFinition”
>在新实体下创建一个属性：“sampleAttribute”
>打开ViewController.swift
>在“import UIKit”下添加“import CoreData”
>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