问题

I know you can save one by using the binary data property of an entity but is it possible to save multiple?

you can save one by using this:

UIImageJPEGRepresentation(image: UIImage)

you can save it and then transform it into an image again with

UIImage(data: ____)

but can I transform an array full of images into binary data?

If you can't with core data, any other ways I can do it?

BTW, the image array is full of user taken image saved on the device..

Thanks for all the helpers!

回答1:

convert your array to NSMutableArray and archive it as NSData

var imgArray = [UIImage]();

var CDataArray = NSMutableArray();

for img in imgArray{
    let data : NSData = NSData(data: UIImagePNGRepresentation(img))
    CDataArray.addObject(data);
}

//convert the Array to NSData
//you can save this in core data
var coreDataObject = NSKeyedArchiver.archivedDataWithRootObject(CDataArray);

after pulling from CData, extract data:

//extract:
if let mySavedData = NSKeyedUnarchiver.unarchiveObjectWithData(coreDataObject) as? NSArray{
    //extract data..
}

Swift 5

There are some methods deprecated now. The following code is working in Swift 5:

func coreDataObjectFromImages(images: [UIImage]) -> Data? {
    let dataArray = NSMutableArray()
    
    for img in images {
        if let data = img.pngData() {
            dataArray.add(data)
        }
    }
    
    return try? NSKeyedArchiver.archivedData(withRootObject: dataArray, requiringSecureCoding: true)
}

func imagesFromCoreData(object: Data?) -> [UIImage]? {
    var retVal = [UIImage]()

    guard let object = object else { return nil }
    if let dataArray = try? NSKeyedUnarchiver.unarchivedObject(ofClass: NSArray.self, from: object) {
        for data in dataArray {
            if let data = data as? Data, let image = UIImage(data: data) {
                retVal.append(image)
            }
        }
    }
    
    return retVal
}

回答2:

Based on daniel-krom's answer I created a swift extension to make it easy to add to model objects:

let coreDataObject = imgArray.coreDataRepresentation()

if let retrievedImgArray = coreDataObject?.imageArray() {
    // use retrievedImgArray
}

Here's the extension

import UIKit

typealias ImageArray = [UIImage]
typealias ImageArrayRepresentation = Data

extension Array where Element: UIImage {
    // Given an array of UIImages return a Data representation of the array suitable for storing in core data as binary data that allows external storage
    func coreDataRepresentation() -> ImageArrayRepresentation? {
        let CDataArray = NSMutableArray()

        for img in self {
            guard let imageRepresentation = UIImagePNGRepresentation(img) else {
                print("Unable to represent image as PNG")
                return nil
            }
            let data : NSData = NSData(data: imageRepresentation)
            CDataArray.add(data)
        }

        return NSKeyedArchiver.archivedData(withRootObject: CDataArray)
    }
}

extension ImageArrayRepresentation {
    // Given a Data representation of an array of UIImages return the array
    func imageArray() -> ImageArray? {
        if let mySavedData = NSKeyedUnarchiver.unarchiveObject(with: self) as? NSArray {
            // TODO: Use regular map and return nil if something can't be turned into a UIImage
            let imgArray = mySavedData.flatMap({
                return UIImage(data: $0 as! Data)
            })
            return imgArray
        }
        else {
            print("Unable to convert data to ImageArray")
            return nil
        }
    }
}

来源：https://stackoverflow.com/questions/32155030/can-you-save-an-array-of-images-in-core-data

标签

arrays