如何在核心数据中按名称保存图像？

Question

I have images in Assets.xcassets named city_00,city_01,...,city_10

I stored them in an array

 let cityImages: [UIImage] = [UIImage(named: "city_00")!,UIImage(named: "city_01")!,.....UIImage(named: "city_10")!]

 let cityNames = ["City A","City B",....., "City J"]

Then I call them using collectionview in my project and allow users to select any city they like

 var imageSelected = [UIImage]()
 var cityImage:UIImage?
var cityImageName:String?

   func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        let cell = collectionView.cellForItem(at: indexPath)
        collectionView.allowsMultipleSelection = false
        cityImage = imageSelected[(indexPath as NSIndexPath).row]
 let selectedImgName = String(format: "%%" ,imageSelected[(indexPath as NSIndexPath).row])
        cityImageName = selectedImgName
}

How do I store the name of city in cityImageName based on image selected?

Answer 1

You should probably use NSValueTransformer to convert your image to NSData and then store the data blob in Core Data. Here is a tutorial that shows how to accomplish this.

If you really want to store it as string (it will take more space because of the encoding) you can have a look at this question on how to base64 encode an image.

Answer 2

It is not advisable to store images into core data. This will lack app in performance.

Converting Image into Base64 string and convert Base64 String into image will take plenty of time.

I would advise you to Store your image into document folder and store that path into your coreData.

This way you can store and retrieve image easily with so much better app performance then storing image into Core Data.

You can use lazy loading as well with this approach will improve app performance further.

As you have stated you have all image in your image asset then just store name of your image in Core data base.

You have image_name stored in cityImages array.

 func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

     let yourRequiredImage:String = cityImages[indexPath.row]// Save this Image name in your core data.
     print (yourRequiredImage)
}

Answer 3

Your cityImages array is an array of images.

Change that to an array of image names instead.

It will use a lot less memory and then in the selected method you can get the image name from the array at the selected index.