Log

Log provides a way to log stuff to the console and to file. It provides the method Log.print() which require minimal changes to your code because you probably already use Swift.print().

Example

This creates a file log output in the default logs directory (path/to/application-support-dir/Logs) with a name containing the current month and year (e.g. log-2018-10.txt for October 2018).

guard let dirURL = Logging.defaultLogsDirectoryURL() else {
    Swift.print("Logs directory not found")
    return
}
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "y-MM"

let fileName = "log-\(dateFormatter.string(from: Date()))"
let fileURL = dirURL.appendingPathComponent(fileName).appendingPathExtension("txt")
let output = FileOutput(filePath: fileURL.path)
Logger.sharedInstance.addOutput(output)

Swift.print("Log file placed at \(fileURL.path)")

You can then start logging using Log.print().

Log.print("Ups, something went wrong")

The log file will look like this

2018-10-29 12:27:11.050 Ups, something went wrong

Attach to emails

If a user reports an issue with your app, you can attach the log files to an email like this.

The following example uses the last 2 log files and attaches them to a mail compose sheet.

let mailController = MFMailComposeViewController()
if let urls = Logging.fileURLs { // returns the log files sorted by the creation date
    let fileManager = FileManager()
    for url in urls.prefix(2) {
        guard let data = fileManager.contents(atPath: url.path) else {
            continue
        }
        // Attach log as text file
        mailController.addAttachmentData(data, mimeType: "text/plain", fileName: url.lastPathComponent)
    }
}