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Redux.dart Middleware that prints the latest action & state

redux_logging #

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Connects a Logger to a Redux Store. Can also simply print the latest state / action changes.

Logs every Action that is dispatched to the Store, along with the current State.

By default, this class does not print anything to your console or send data to a web service, such as Fabric or Sentry. It simply logs entries to a Logger instance.

If you simply want to print the latest action and state to your console / terminal, create a new LoggingMiddleware.printer() and pass it to your Store upon creation.

If you want more control over where the logged data is sent, you can listen to your Logger's onRecord Stream.

Dart Versions #

  • Dart 1 support: 0.1.x
  • Dart 2 Support: 0.2.x+

Simple Printing example #

If you just want an easy way to print actions to your console / terminal as they are dispatched, use the new LoggingMiddleware.printer() factory.

Note: The LoggingMiddleware needs be the LAST middleware in the list.

import "package:redux/redux.dart";
import 'package:redux_logging/redux_logging.dart';

final store = new Store<int>(
  (int state, dynamic action) => state + 1,
  initialValue: 0,
  // Note the LoggingMiddleware should come last in the list of Middleware!
  middleware: [myOtherMiddleware, new LoggingMiddleware.printer()]

store.dispatch("Hi"); // prints {Action: "Hi", Store: 1, Timestamp: ...}

Example #

If you only want to log actions to a Logger, and choose how to handle the output, use the default constructor.

import 'package:logging/logging.dart';
import "package:redux/redux.dart";
import 'package:redux_logging/redux_logging.dart';

// Create your own Logger
final logger = new Logger("Redux Logger");

// Pass it to your Middleware
final middleware = new LoggingMiddleware(logger: logger);
final store = new Store<int>(
  (int state, dynamic action) => state + 1,
  initialState: 0,
  middleware: [middleware],

// Note: One quirk about listening to a logger instance is that you're
// actually listening to the Singleton instance of *all* loggers.
  // Filter down to [LogRecord]s sent to your logger instance
  .where((record) => record.loggerName ==
  // Print them out (or do something more interesting!)
  .listen((loggingMiddlewareRecord) => print(loggingMiddlewareRecord));

Formatting the log message #

This library includes two formatters out of the box:

  • LoggingMiddleware.singleLineFormatter
  • LoggingMiddleware.multiLineFormatter

You can optionally control the format of the message that will be logged by implementing your own MessageFormatter and passing it to the LoggingMiddleware constructor. It is a simple function that takes three parameters: the State, Action, and Timestamp.

Formatting Example #

import "package:redux/redux.dart";
import 'package:redux_logging/redux_logging.dart';

// Create a formatter that only prints out the dispatched action
String onlyLogActionFormatter<State>(
  State state,
  dynamic action,
  DateTime timestamp,
) {
  return "{Action: $action}";

// Create your middleware using the formatter.
final middleware = new LoggingMiddleware(formatter: onlyLogActionFormatter);

// Add the middleware with your formatter to your Store
final store = new Store<int>(
  (int state, dynamic action) => state + 1,
  initialState: 0,
  middleware: [middleware],
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Redux.dart Middleware that prints the latest action & state

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Icon for licenses.MIT (LICENSE)


logging, redux


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