SwiftUI - 如何将选定的图像保存到 CoreData 并从另一个视图中检索它

Question

我正在使用允许用户上传个人资料图片的图像选择器。但是我不知道如何在选择后保存图像。这是我正在使用的图像选择器代码。保存后，我还想在另一个视图中检索图像并显示它。

image!
    .resizable()
    .aspectRatio(contentMode: .fill)
    .frame(width: 150, height: 150)
    .clipShape(Circle())
    .overlay(Circle().stroke(Color.white, lineWidth: 4))
    .shadow(radius: 10)
    .onTapGesture { self.shouldPresentActionScheet = true }
    .sheet(isPresented: $shouldPresentImagePicker) {
        SUImagePickerView(sourceType: self.shouldPresentCamera ? .camera : .photoLibrary, image: self.$image, isPresented: self.$shouldPresentImagePicker)
    }.actionSheet(isPresented: $shouldPresentActionScheet) { () -> ActionSheet in
        ActionSheet(title: Text("Choose mode"), message: Text("Please choose your preferred mode to set your profile image"), buttons: [ActionSheet.Button.default(Text("Camera"), action: {
            self.shouldPresentImagePicker = true
            self.shouldPresentCamera = true
        }), ActionSheet.Button.default(Text("Photo Library"), action: {
            self.shouldPresentImagePicker = true
            self.shouldPresentCamera = false
        }), ActionSheet.Button.cancel()])
        
    }

Answer 1

将图像保存到 Core Data 不是一个好习惯，因为您需要在保存数据时将其编码为数据，并在检索时从数据中解码。另外，我读过存在性能问题。最佳实践是使用本地存储来保存图像，Core Data 在存储中保存图像的路径。可以这样完成。最好设置一个唯一的图像名称，如 UUID()

func saveToDocumentDirectory(imageId: String) {
        if let image = takenImage, let data = image.jpegData(compressionQuality: 0.7) {
            do {
                let filename = getDocumentsDirectory().appendingPathComponent(imageId)
                try data.write(to: filename, options: [[.atomicWrite, .completeFileProtection]])
            } catch {
                print("error saving data")
            }
        }
    }

您可以在创建 Core Data 对象时调用此函数，例如

saveToDocumentDirectory(imageId: object.id.uuidString)

可以用这个方法获取图片：

func retrieveImage(with id: UUID) {
    let dummyImage = Image(systemName: "person")
        do {
            let filename = getDocumentsDirectory().appendingPathComponent(id.uuidString)
            let data = try Data(contentsOf: filename)
            if let uiImage = UIImage(data: data) {
                return Image(uiImage: uiImage)
            }
        } catch {
            print("error loading data")
            return dummyImage
        }
        return dummyImage
}

尝试使用此图像选择器

import SwiftUI

struct ImagePicker: UIViewControllerRepresentable {
    @Environment(\.presentationMode) var presentationMode
    @Binding var takenPicture: UIImage?
    
    class Coordinator: NSObject, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
        var parent: ImagePicker
        
        init(_ parent: ImagePicker) {
            self.parent = parent
        }

        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
            if let image = info[.originalImage] as? UIImage {
                parent.takenPicture = image
            }

            parent.presentationMode.wrappedValue.dismiss()
        }
    }
    
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: Context) -> UIImagePickerController {
        let picker = UIImagePickerController()
        picker.sourceType = .camera
        picker.allowsEditing = false
        picker.cameraFlashMode = UIImagePickerController.CameraFlashMode.off
        picker.delegate = context.coordinator
        return picker
    }
    
    func updateUIViewController(_ uiViewController: UIImagePickerController, context: Context) {}
}