# Logger

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Small, easy to use and extensible logger which prints beautiful logs.<br>
Inspired by [logger](https://github.com/orhanobut/logger) for Android.

**Show some ❤️ and star the repo to support the project**

### Resources:

- [Documentation](https://pub.dev/documentation/logger/latest/logger/logger-library.html)
- [Pub Package](https://pub.dev/packages/logger)
- [GitHub Repository](https://github.com/SourceHorizon/logger)

## Getting Started

Just create an instance of `Logger` and start logging:

```dart
var logger = Logger();

logger.d("Logger is working!");
```

Instead of a string message, you can also pass other objects like `List`, `Map` or `Set`.

## Output

![](https://raw.githubusercontent.com/SourceHorizon/logger/main/art/screenshot.png)

# Documentation

## Log level

You can log with different levels:

```dart
logger.t("Trace log");

logger.d("Debug log");

logger.i("Info log");

logger.w("Warning log");

logger.e("Error log", error: 'Test Error');

logger.f("What a fatal log", error: error, stackTrace: stackTrace);
```

To show only specific log levels, you can set:

```dart
Logger.level = Level.warning;
```

This hides all `trace`, `debug` and `info` log events.

## Options

When creating a logger, you can pass some options:

```dart
var logger = Logger(
  filter: null, // Use the default LogFilter (-> only log in debug mode)
  printer: PrettyPrinter(), // Use the PrettyPrinter to format and print log
  output: null, // Use the default LogOutput (-> send everything to console)
);
```

If you use the `PrettyPrinter`, there are more options:

```dart
var logger = Logger(
  printer: PrettyPrinter(
      methodCount: 2, // Number of method calls to be displayed
      errorMethodCount: 8, // Number of method calls if stacktrace is provided
      lineLength: 120, // Width of the output
      colors: true, // Colorful log messages
      printEmojis: true, // Print an emoji for each log message
      // Should each log print contain a timestamp
      dateTimeFormat: DateTimeFormat.onlyTimeAndSinceStart,
  ),
);
```

### Auto detecting

With the `io` package you can auto detect the `lineLength` and `colors` arguments.
Assuming you have imported the `io` package with `import 'dart:io' as io;` you
can auto detect `colors` with `io.stdout.supportsAnsiEscapes` and `lineLength`
with `io.stdout.terminalColumns`.

You should probably do this unless there's a good reason you don't want to
import `io`, for example when using this library on the web.

## LogFilter

The `LogFilter` decides which log events should be shown and which don't.<br>
The default implementation (`DevelopmentFilter`) shows all logs with `level >= Logger.level` while
in debug mode (i.e., running dart with `--enable-asserts`).
In release mode all logs are omitted.

You can create your own `LogFilter` like this:

```dart
class MyFilter extends LogFilter {
  @override
  bool shouldLog(LogEvent event) {
    return true;
  }
}
```

This will show all logs even in release mode. (**NOT** a good idea)

## LogPrinter

The `LogPrinter` creates and formats the output, which is then sent to the `LogOutput`.<br>
You can implement your own `LogPrinter`. This gives you maximum flexibility.

A very basic printer could look like this:

```dart
class MyPrinter extends LogPrinter {
  @override
  List<String> log(LogEvent event) {
    return [event.message];
  }
}
```

If you created a cool `LogPrinter` which might be helpful to others, feel free to open a pull
request.
:)

### Colors

Please note that in some cases ANSI escape sequences do not work under macOS.
These escape sequences are used to colorize the output.
This seems to be related to a Flutter bug that affects iOS builds:
https://github.com/flutter/flutter/issues/64491

However, if you are using a JetBrains IDE (Android Studio, IntelliJ, etc.)
you can make use of
the [Grep Console Plugin](https://plugins.jetbrains.com/plugin/7125-grep-console)
and the [`PrefixPrinter`](/lib/src/printers/prefix_printer.dart)
decorator to achieve colored logs for any logger:

```dart
var logger = Logger(
    printer: PrefixPrinter(PrettyPrinter(colors: false))
);
```

## LogOutput

`LogOutput` sends the log lines to the desired destination.<br>
The default implementation (`ConsoleOutput`) send every line to the system console.

```dart
class ConsoleOutput extends LogOutput {
  @override
  void output(OutputEvent event) {
    for (var line in event.lines) {
      print(line);
    }
  }
}
```

Other provided `LogOutput`s are:

* `FileOutput`/`AdvancedFileOutput`
* `StreamOutput`

Possible future `LogOutput`s could send to Firebase or to Logcat. Feel free to open pull
requests.

# Acknowledgments

This package was originally created by [Simon Choi](https://github.com/simc), with further
development by [Harm Aarts](https://github.com/haarts), greatly enhancing its functionality over
time. 
