Small, easy to use and extensible logger which prints beautiful logs.
Inspired by logger for Android.
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Just create an instance of Logger and start logging:
var logger = Logger();
logger.d("Logger is working!");Instead of a string message, you can also pass other objects like List, Map or Set.
You can log with different levels:
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:
Logger.level = Level.warning;This hides all trace, debug and info log events.
When creating a logger, you can pass some options:
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:
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,
),
);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.
The LogFilter decides which log events should be shown and which don't.
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:
class MyFilter extends LogFilter {
@override
bool shouldLog(LogEvent event) {
return true;
}
}This will show all logs even in release mode. (NOT a good idea)
The LogPrinter creates and formats the output, which is then sent to the LogOutput.
You can implement your own LogPrinter. This gives you maximum flexibility.
A very basic printer could look like this:
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.
:)
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: flutter/flutter#64491
However, if you are using a JetBrains IDE (Android Studio, IntelliJ, etc.)
you can make use of
the Grep Console Plugin
and the PrefixPrinter
decorator to achieve colored logs for any logger:
var logger = Logger(
printer: PrefixPrinter(PrettyPrinter(colors: false))
);LogOutput sends the log lines to the desired destination.
The default implementation (ConsoleOutput) send every line to the system console.
class ConsoleOutput extends LogOutput {
@override
void output(OutputEvent event) {
for (var line in event.lines) {
print(line);
}
}
}Possible future LogOutputs could send to a file, firebase or to Logcat. Feel free to open pull
requests.
This package was originally created by Simon Choi, with further development by Harm Aarts, greatly enhancing its functionality over time.
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