如何在OSX Swift中从message：// URL获取电子邮件主题

事实证明，我将目录的内容误解draggingInfo.draggingPasteboard().types为仅包含一种类型的信息（在这种情况下为URL）的层次列表。必须订阅拖动的事件类型kUTTypeMessage as String并使用以下命令从粘贴板中检索电子邮件主题stringForType("public.url-name")

编辑：请注意，当您拖动电子邮件线程时，当前Mail.app有时会创建一堆邮件。尽管上面的方法仍然可以获取堆栈的主题，但是拖动信息中没有URL，并且由于没有可用的Message-ID列表，我不得不求助于用户的mbox目录：

        // See if we can resolve e-mail message meta data
        if let mboxPath = pboard.stringForType("com.apple.mail.PasteboardTypeMessageTransfer") {
            if let automatorPlist = pboard.propertyListForType("com.apple.mail.PasteboardTypeAutomator") {
                // Get the latest e-mail in the thread
                if let maxID = (automatorPlist.allObjects.flatMap({ $0["id"]! }) as AnyObject).valueForKeyPath("@max.self") as? Int {
                    // Read its meta data in the background
                    let emailItem = draggingEmailItem
                    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
                        // Find the e-mail file
                        if let path = Util.findEmlById(searchPath: mboxPath, id: maxID) {
                            // Read its contents
                            emailItem.properties = Util.metaDataFromEml(path)
                            dispatch_async(dispatch_get_main_queue(), {
                                // Update UI
                            });
                        }
                    }
                }
            }
        }

有用的功能：

/* Searches the given path for <id>.eml[x] and returns its URL if found
 */
static func findEmlById(searchPath searchPath: String, id: Int)-> NSURL? {
    let enumerator = NSFileManager.defaultManager().enumeratorAtPath(searchPath)
    while let element = enumerator?.nextObject() as? NSString {
        switch (element.lastPathComponent, element.pathExtension) {
            case (let lpc, "emlx") where lpc.hasPrefix("\(id)"):
                return NSURL(fileURLWithPath: searchPath).URLByAppendingPathComponent(element as String)!
            case (let lpc, "eml") where lpc.hasPrefix("\(id)"):
                return NSURL(fileURLWithPath: searchPath).URLByAppendingPathComponent(element as String)!
            default: ()
        }
    }
    return nil
}

/* Reads an eml[x] file and parses it, looking for e-mail meta data
 */
static func metaDataFromEml(path: NSURL)-> Dictionary<String, AnyObject> {

    // TODO Support more fields

    var properties: Dictionary<String, AnyObject> = [:]
    do {
        let emlxContent = try String(contentsOfURL: path, encoding: NSUTF8StringEncoding)
        // Parse message ID from "...\nMessage-ID: <...>"
        let messageIdStrMatches = emlxContent.regexMatches("[\\n\\r].*Message-ID:\\s*<([^\n\r]*)>")
        if !messageIdStrMatches.isEmpty {
            properties["messageId"] = messageIdStrMatches[0] as String
        }
    }
    catch {
        print("ERROR: Failed to open emlx file")
    }
    return properties
}

注意：如果您的应用是沙盒，则需要将com.apple.security.temporary-exception.files.home-relative-path.read-only权利设置为其中包含一个字符串的数组：/Library/