Simple logging for simples needs.
Declare your dependency in your Package.swift file.
.package(name: "Logger", url: "https://github.com/nativedevbr/swift-log.git", from: "0.1.0"),and add it to your application target.
.target(name: "BestExampleApp", dependencies: ["Logger"]),Now, let's learn how to use it.
// Import the logger package.
import Logger
// Create a logger instance, the system is a string that identifies this logging instance.
// It's recommended to use an inverse domain like your bundle identifier.
// This logging implementation is based on destinations, each destination represent a place where
// the log messagens will be sent.
let logger = Logger(system: "br.dev.native.best-example-app", destinations: [.console(), .file(url: URL(...)])
// Then, just call the available methods on the logger instance, there is one method for each
// logging level. [verbose, debug, info, warning and error].
logger.info("Hello World!")
// There's support for adding additional context to a log message.
logger.error("something is not working", context: ["user_id": "deadbeef"])If you prefer, there's possibility for defining a shared logger instance through Logger.main.
Logger.main = Logger(system: "br.dev.native.best-example-app", destinations: [.console(), .file(url: URL(...)])If Logger.main is used before being initialized the app will crash.
This package provides three destinations out of the box, the console, file and sqlite.
The console destination sends the log messages to the console and it's debug only, so no logs are sent on release builds.
The file destination writes logs messages to a local file that the user must provide.
And the sqlite destination writes logs to a sqlite database, this is the most powerful destination as you can aggregate and query for logs.
Boths destinations accepts a Formatter parameter to customize the formatting logic of the message, there's a default implementation.
There is a default implementaiton for a SQLite destination that supports filtering log messages.
// Initialize a new SQLiteLoggingStore passing the database path.
// It's important to keep a single instance of a SQLiteLoggingStore through the whole life cycle.
let store = try SQLiteLoggingStore(path: "path/to/db.sqlite")
// Init a Logger instance by passing the store's destination
let logger = Logger(
system: "br.dev.native.logger.tests",
destinations: [store.destination]
)
// Use the logger
logger.info("info message")
// And then query the log messages by using method `logs(where:)`.
let logs = try store.logs(
where: .or(.level(.info), .level(.error)), .file("%Tests.swift"))
// The above filter is transformed into a SQL `where` clause and stands for:
// 'Fetch all log messages that has a level error or info and has happened on files that ends with "Tests.swift"'.
// Example: 'WHERE ("level" = 2 OR "level" = 4) AND ("file" LIKE "%Tests.swift")'For available filters, take a look at the Filter enum.
This destination approach makes very easy to add new ones, like this example of a destination that sends the log messages to Crashlytics.
import FirebaseCrashlytics
extension Logger.Destination {
static let crashlytics = Logger.Destination { msg in
// You can use the default formatter for generating a string,
// or implement your own formatting logic.
let string = Logger.Formatter.default.format(msg)
Crashlytics.crashlytics().log(string)
}
}
// Then to use the new destination, simply init a logger passing the `crashlytics` destination.
Logger.main = Logger(system: "br.dev.native.best-example-app", destinations: [.console(), .crashlytics])Pull requests are welcome.
Please make sure to update tests as appropriate.