MELogger

Installation

You can install the package under your Project / Package Dependencies settings. Or if you are specifying it as a dependency for another package you can add the dependency in Package.swift:

//...
dependencies: [
    .package(
        url: "[email protected]:Mono-Empire/MELogger.git",
        from: Version("3.0.0")
    )
],
targets: [
    .target(
        name: "YourProject",
        dependencies: [
            .product(
                name: "MELogger",
                package: "MELogger"
            ),
        ]
    ),
    //...
]
//...

Basic usage

Provides a generalized logging interface very similar to SwiftLog. Allows logging to console, to a file, or to any other custom destination (such as a cloud service, Slack, etc.).

Usage is simple:

// Instantiate a Logger (perhaps as a global constant, but that's up to you)
let logger = Logger(label: "com.example.mybundle")
// ...by default messages will be logged to the console.

// Log a message, specifying the log-level with the appropriate method:
logger.warning("This is a warning")
// ...you can add some meta-data too:
logger.notice("This is just a notice", metadata: ['class': 'MyClassName'])

// For all levels you can also pass an optional `Error` (though obviously more common for things like `error` or `critical`)
logger.error("Something bad happened!", error: err)

You have the following available levels:

• trace
• debug
• info
• notice
• warning
• error
• critical

Specify log destinations

Each logger instance can be set up with one or more logging destinations - so for example, log messages can be sent to both the console and to a log file. For each destination you can set what level to log, and also a number of other destination-specific settings like log file size and rotation preferences.

Here's an example of setting up logging to a file:

// Create a file logger (see the in-code documentation for more settings)
let settings = FileLoggerDestination.Settings(logFileSizeLimit: 300, logFileRotationsKept: 2)
let fileLoggerDestination = FileLoggerDestination(settings: settings)

// Add the destination to an existing logger instance...
logger.destinationManager.add(fileLoggerDestination)

// ...or you can add the destination to all logger instances:
MELoggerDestinationManager.shared.add(fileLoggerDestination)

The destination object also provides useful methods to manage log files:

// Get all the log files
let logFiles = fileLoggerDestination.getLogFiles()

// Clear the log files
fileLoggerDestination.clearLogFiles()

Built-in log destinations

By default, MELogger provides a set of useful logging destinations out of the box:

• ConsoleLoggerDestination - logs messages to the standard console; supports a formatted output, message truncating, etc.
• FileLoggerDestination - saves log messages to a file; supports file rotation, maximum file sizes, etc.
• CrashlyticsLoggerDestination - sends your logs to Crashlytics (see custom log destinations explanation below)
• AssertionFailureDestination - triggers an assertionFailure (which will pause execution in Xcode's Debug mode) with the logged message; great for surfacing errors instead of just having them silently fail in the logs
• MockLoggerDestination - a destination aimed at unit testing (see the section below for more info)

See the Settings of each destination for more info on what each supports.

Custom log destinations

You can also write your own custom logging destinations, such as logging to a cloud service. Simply implement a new struct that conforms to MELoggerDestination.

As an example, see CrashlyticsLoggerDestination here. Not all of your packages will have Crashlytics dependencies, but it is enough to just to add the CrashlyticsLoggerDestination once to your shared destinations:

// For example, in your AppDelegate's didFinishLaunchingWithOptions...

// Initialize Firebase
FirebaseApp.configure()

// Add Crashlytics destination
MELoggerDestinationManager.shared.add(CrashlyticsLoggerDestination())

Now that you have CrashlyticsLoggerDestination as a shared destination even the relevant log messages from sub-packages that do not have Firebase dependencies will be sent to Crashlytics.

Testing with MockLoggerDestination

In certain cases it may be useful to test error cases in your code using the MockLoggerDestination. This log destination allows you to access any previous log messages for your assertions. For example in your tests:

// ExampleTests.swift

// Create and add mock destination
let mockLogDestination = MockLogDestination()
MELoggerDestinationManager.shared.removeAll()
MELoggerDestinationManager.shared.add(mockLogDestination)

// Do something illegal
let myExample = Example()
myExample.doSomethingThatTriggersWarning()

// Check if it was illegal
XCTAssertEqual(anotherMockLogDestination.lastLoggedLevel, .warning)
XCTAssertFalse(anotherMockLogDestination.loggedMessages.isEmpty)
XCTAssertEqual(anotherMockLogDestination.lastLoggedMessage, "The warning message")