Core Data数据操作

1.建立学生实体，插入100条数据

2.按条件查询学生数据

3.统计学生信息

4.修改学生信息

5.删除学生数据

import UIKit

import CoreData

class ViewController: UIViewController {

override func viewDidLoad() {

super.viewDidLoad()

//1.建立模型文件

//2.建立CoreDataStack

//3.设置AppDelegate

//插入数据

insertStudents()

//查询数据

fetchStudents()

//统计信息

countStudents()

//修改数据

updateStudents()

//删除数据

deleteStudents()

}

}

extension ViewController{

func insertStudents(){

let strs1 = ["a","b","c","d","e","f","g","h","i","j"]

let strs2 = ["01","02","03","04","05","06","07","08","09","10"]

for i in 0..<100 {

let sno = "\(1001+i)"

let name = strs1[i/10] + strs2[i%10]

let score = i

insertStudent(sno: sno, name: name, score: score)

}

CoreDataStack.defaultStack().saveContext()

}

func insertStudent(sno sno:String,name:String,score:Int){

let context = CoreDataStack.defaultStack().context

let student = NSEntityDescription.insertNewObjectForEntityForName("student", inManagedObjectContext: context) as! Student

student.sno = sno

student.name = name

student.score = score

}

func fetchStudents(){

let context=CoreDataStack.defaultStack().context

let request=NSFetchRequest(entityName:"Student")

let sort = NSSortDescriptor(key:"sno", ascending:true, selector:"localizedStandardCompare")

request.sortDescriptors = [sort]

//request.predicate = NSPredicate(format:"score > 60")

//request.predicate = NSPredicate(format:"name like 'a*'")

do{

let students=(try context.executeFetchRequest(request)) as! [Student]

for student in students{

print("\(student.sno!),\(student.name!),\(student.score!)")

}

}catch{

print("Fetch failed")

}

}

func countStudents(){

//        let context = CoreDataStack.defaultStack().context

//

//        let request = NSFetchRequest(entityName:"Student")

//        request.predicate = NSPredicate(format:"score > 90")

//        request.resultType = CountResultType

//

//        do {

//            let entries = (try context.executeFetchRequest(request))

//            let count = entries.first!.integerValue

//            print("Count:\(count)")

//        }catch{

//            print("Fetch failed......")

//        }

let context = CoreDataStack.defaultStack().context

let request=NSFetchRequest(entityName:"Student")

request.resultType = .DictionaryResultType

let description = NSExpressionDescription()

description.name="AverageScore"

let args=[NSExpression(forKeyPath:"score")]

description.expression = NSExpression(forFunction: "average", arguments:args)

description.expressionResultType = .FloatAttributeType

do {

let entries = (try context.executeFetchRequest(request))

let result=entries.first! as! NSDictionary

let averageScore = result["AverageScore"]!

print("Average:\(averageScore)")

}catch{

print("Fetch failed......")

}

}

func updateStudents(){

let context=CoreDataStack.defaultStack().context

let request = NSFetchRequest(entityName:"Student")

request.predicate = NSPredicate(format:"name like 'a*'")

do{

let students = (try context.executeFetchRequest(request)) as! [Student]

for student in students{

student.score = 100

}

}catch{

print("Fetch failed")

}

CoreDataStack.defaultStack().saveContext()

}

func deleteStudents(){

let context = CoreDataStack.defaultStack().context

let request=NSFetchRequest(entityName:"Student")

request.predicate = NSPredicate(format:"score < 60")

do{

let students = (try context.executeFetchRequest(request)) as! [Student]

for student in students{

context.deleteObject(student)

}

}catch{

print("Fetch failed......")

}

CoreDataStack.defaultStack().saveContext()

}

}