我正在为丰富的通知添加缩略图。我生成的图像用作附件，如下所示：
let url = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)
let fileURL = url.appendingPathComponent("someImageName", isDirectory: false).appendingPathExtension("png")
do{
try UIImagePNGRepresentation(image)?.write(to: fileURL)
}catch{
print("Could not write: ", error)
}
这很成功。如果我现在运行此代码：
let content = try? FileManager.default.contentsOfDirectory(atPath: NSTemporaryDirectory())
print(content ?? "error")
它打印出来：["someImageName.png"]。
然后我创建附件，如下所示：
let attachment = try? UNNotificationAttachment(identifier: "image", url: url, options: nil)
let content = UNMutableNotificationContent()
content.title = "Test"
content.attachments = [attachment!]
let request = UNNotificationRequest(identifier: "someID", content:content, trigger: /*someTrigger*/)
UNUserNotificationCenter.current().add(request, withCompletionHandler:...)
这一切都有效。通知已发送，附件已附加。但是，如果我现在打印出临时文件夹的内容，它就是空的！我之前保存的图像已从此文件夹中删除。
经过大量的反复试验，我发现在添加通知的时候图像被删除了。为什么我的通知会删除我的图片？我找不到任何关于此的文档！
如果我执行上述所有操作，但注释掉这一行：//content.attachments = [attachment!]，意味着我的存储图像不会作为附件添加到我的通知中，那么我的图像不会从临时文件夹中删除！
这些文件在使用后是否被清理？或者在通知消失后我是否必须查看其他文件夹并手动清理它们？我不希望我的应用程序创建数百个永远不会再次使用的图像，而无法删除它们。
这些天我面临同样的问题，答案在文档中，一见钟情不是很容易看到但是它在那里：
关于UNNotificationAttachment：
...一旦经过验证，附加文件就会被移动到附件数据存储中，以便所有适当的进程都可以访问它们。位于应用程序包中的附件将被复制而不是移动。
关于init方法：
当您安排包含附件的通知请求时，附件的文件将移动到新位置，以方便相应进程的访问。移动后，访问该文件的唯一方法是使用UNUserNotificationCenter对象的方法。
所以我决定：
像你一样编写文件并在NSTemporaryDirectory()中写了一个副本我用这个例子轻松创建和删除TempDirectory（Swift 4.0）（感谢Ole Begemman）：
import Foundation
/// A wrapper around a temporary file in a temporary directory. The directory
/// has been especially created for the file, so it's safe to delete when you're
/// done working with the file.
///
/// Call `deleteDirectory` when you no longer need the file.
struct TemporaryFile {
let directoryURL: URL
let fileURL: URL
/// Deletes the temporary directory and all files in it.
let deleteDirectory: () throws -> Void
/// Creates a temporary directory with a unique name and initializes the
/// receiver with a `fileURL` representing a file named `filename` in that
/// directory.
///
/// - Note: This doesn't create the file!
init(creatingTempDirectoryForFilename filename: String) throws {
let (directory, deleteDirectory) = try FileManager.default
.urlForUniqueTemporaryDirectory()
self.directoryURL = directory
self.fileURL = directory.appendingPathComponent(filename)
self.deleteDirectory = deleteDirectory
}
}
extension FileManager {
/// Creates a temporary directory with a unique name and returns its URL.
///
/// - Returns: A tuple of the directory's URL and a delete function.
/// Call the function to delete the directory after you're done with it.
///
/// - Note: You should not rely on the existence of the temporary directory
/// after the app is exited.
func urlForUniqueTemporaryDirectory(preferredName: String? = nil) throws
-> (url: URL, deleteDirectory: () throws -> Void)
{
let basename = preferredName ?? UUID().uuidString
var counter = 0
var createdSubdirectory: URL? = nil
repeat {
do {
let subdirName = counter == 0 ? basename : "\(basename)-\(counter)"
let subdirectory = temporaryDirectory
.appendingPathComponent(subdirName, isDirectory: true)
try createDirectory(at: subdirectory, withIntermediateDirectories: false)
createdSubdirectory = subdirectory
} catch CocoaError.fileWriteFileExists {
// Catch file exists error and try again with another name.
// Other errors propagate to the caller.
counter += 1
}
} while createdSubdirectory == nil
let directory = createdSubdirectory!
let deleteDirectory: () throws -> Void = {
try self.removeItem(at: directory)
}
return (directory, deleteDirectory)
}
}
使用TempURL附加文件后，文件将被移动，您可以删除TempDirectory。
稍后进行一些测试并确定，我终于发现我的文件（在我的情况下是一个图像）存储在这里：
URL: file:///var/mobile/Library/SpringBoard/PushStore/Attachments/com.YourApp.Name/8e52c6673f6e735f83535486bf750ba1118a3ade.png
在显示或清理通知中心后，文件将被删除。
为什么这一切？ - >沙盒！当我将文件附加到触发器（这里为我的UNCalendarNotificationTrigger）时，我将负责我的文件的Calendar命名为在我的通知中显示它，但是为了处理它，它必须将文件放在HIS目录中。
希望它有所帮助，我花了一段时间才找到所有神秘感！