你能在核心数据中保存一组图像吗？

Question

我知道您可以使用实体的二进制数据属性保存一个，但是可以保存多个吗？

你可以用这个节省一个：

UIImageJPEGRepresentation(image: UIImage)

您可以保存它，然后使用

再次将其转换为图像

UIImage(data: ____)

但是我可以将充满图像的数组转换为二进制数据吗？

如果你不能用核心数据，我还有其他方法吗？

顺便说一句，图像数组中全是用户拍摄的保存在设备上的图像..

感谢大家的帮助！

Answer 1

将您的数组转换为 NSMutableArray 并将其存档为 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);

从 CData 拉取后，提取数据：

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

Swift 5

有些方法现已弃用。以下代码适用于 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
}

Answer 2

根据 daniel-krom 的回答，我创建了一个 swift 扩展，以便轻松添加到模型对象：

let coreDataObject = imgArray.coreDataRepresentation()

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

这是扩展名

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: [=11=] as! Data)
            })
            return imgArray
        }
        else {
            print("Unable to convert data to ImageArray")
            return nil
        }
    }
}

你能在核心数据中保存一组图像吗？

Can you save an array of images in core data?

arrays

store

image

swift

ios8

Swift 5