[日本語]
You can do database programming by Core Data, O/R mapping tool for Sqlite, on iOS.
Environment: Xcode 8.3, Swift 3
1.Preparation
At first, Check "Use Core Data" when project is created.
And code of Core Data Objects are created in AppDelegate.
Next, select "[project name].xcdatamodeld" and define table layout.
To save UIImage, select "Binary Data" in Type and check "Allow External Storage".
When the size of UIImage is big, URL of UIImage is saved in Core Data.
When you don't check "Allow External Storage", the time of saving core data will take and memory utilization will be increase instantly, and an application will crash.
After table layout definition, execute [Editor]-[Create NSManagedObject Subclass] on Xcode.
And class of table layout definition, NSManagedObject is created.
At last, declare "import Core Data" at the top of class using Core Data.
2.How to INSERT
At first, Make NSManagedObjectContext in AppDelegate.
Next, Make NSManagedObject from NSManagedObjectContext.
Let's see code for inserting new data by Core Data.
import UIKit
import CoreData
class ViewController: UIViewController {
private var imageView:Array<UIImageView!> = Array<UIImageView!>()
func saveImageData(){
//Save UIImageView's image
let imageData:NSData! = UIImageJPEGRepresentation(imageView[0].image,1.0)!
var imageOrientation:Int = 0
if (imageView[0].image.imageOrientation == UIImageOrientation.Down){
imageOrientation = 2
}else{
imageOrientation = 1
}
let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext
let objectEntity:NSManagedObject = NSEntityDescription.insertNewObjectForEntityForName("Object", inManagedObjectContext: managedContext) as NSManagedObject
objectEntity.setValue(imageData, forKey: "dataValue")
objectEntity.setValue(imageOrientation, forKey: "imageOrientation")
do {
try managedContext.save()
}catch let error{
NSLog("\(error)")
}
managedContext.reset()
}
}
2.How to SELECT
Let's see code for selecting data by Core Data.
func LoadData(id:String){
var minX:CGFloat = 0
var minY:CGFloat = 0
var widthValue:CGFloat = 0
var heightValue:CGFloat = 0
var imageOrientation:Int = 0
let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Object")
fetchRequest.returnsObjectsAsFaults = false
let predicate = NSPredicate(format: "id == %@", id)
fetchRequest.predicate = predicate
let descriptor_1 = NSSortDescriptor(key: "objectType", ascending: true)
let descriptor_2 = NSSortDescriptor(key: "createDateTime", ascending: false)
fetchRequest.sortDescriptors = [descriptor_1,descriptor_2]
do {
let fetchResults: Array = try managedContext.executeFetchRequest(fetchRequest)
for fetchResult in fetchResults {
let object = fetchResult as! NSManagedObject
width = fetchResult.valueForKey("width") as! CGFloat
height = fetchResult.valueForKey("height") as! CGFloat
minX = fetchResult.valueForKey("minX") as! CGFloat
minY = fetchResult.valueForKey("minY") as! CGFloat
data = fetchResult.valueForKey("data") as! NSData
image = UIImage(data: data)
imageOrientation = fetchResult.valueForKey("imageOrientation") as! Int
if (imageOrientation == 2) {
image = UIImage(CGImage: image!.CGImage!, scale: image!.scale, orientation: UIImageOrientation.Down)
}
imageView.append(UIImageView())
imageView[imageView.count - 1].frame = CGRect(x:minX,y:minY,width:widthValue,height:heightValue)
imageView[imageView.count - 1].image = image
self.view.addSubView(imageView[imageView.count-1])
}
}catch let error{
NSLog("\(error)")
}
managedContext.reset()
}
Use NSPredicate for designating searching options.
Use NSSortDescriptor and ascending option for designation sort options.
If you road UIImage, check UIImageOrientation.
If UIImageOrientation is down, you must invert UIImage.
3.How to UPDATE
Update value of data which is read.
Let's see code for updating data by Core Data.
func UpdateData(id:String, objectType:Int){
var index:Int = 0
let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Object")
fetchRequest.returnsObjectsAsFaults = false
let predicate = NSPredicate(format: "id == %@ And objectType == %d", id, objectType)
fetchRequest.predicate = predicate
do {
let fetchResults: Array = try managedContext.executeFetchRequest(fetchRequest)
for fetchResult in fetchResults {
let object = fetchResult as! NSManagedObject
//Get value
index = fetchResult.valueForKey("index") as! Int
//Update value
object.setValue(imageView[index].frame.width, forKey: "width")
object.setValue(imageView[index].frame.height, forKey: "height")
object.setValue(imageView[index].frame.minX, forKey: "minX")
object.setValue(imageView[index].frame.minY, forKey: "minY")
let imageData:NSData! = UIImageJPEGRepresentation(imageView[index].image,1.0)!
object.setValue(imgeData, forKey: "data")
var imageOrientation:Int = 0
if (imageView[index].image.imageOrientation == UIImageOrientation.Down){
imageOrientation = 2
}else{
imageOrientation = 1
}
object.setValue(imageOrientation, forKey:"imageOrientation")
}
try managedContext.save()
}catch let error{
NSLog("\(error)")
}
managedContext.reset()
}
4.How to DELETE
Delete data which is read.
func DeleteData(id:String,objectType:Int){
let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext: NSManagedObjectContext! = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Object")
fetchRequest.returnsObjectsAsFaults = false
let predicate = NSPredicate(format: "id == %@ and objectNo == %d", id,objectType)
fetchRequest.predicate = predicate
do {
var fetchResults: Array! = try managedContext.executeFetchRequest(fetchRequest)
for fetchResult in fetchResults {
let object = fetchResult as! NSManagedObject
//Making a mark as deleted
managedContext.deleteObject(object)
}
//Exec saving -> Delete data
try managedContext.save()
}catch let error{
NSLog("\(error)")
}
managedContext.reset()
}
