slack-messages.dart

import 'dart:convert' show utf8;
import 'dart:convert' show json;

import 'dart:io';

class SlackMessage {
  final String? inChannel;
  final String? message;

  const SlackMessage({
    required this.inChannel,
    required this.message,
  });

  Future<bool> send(String webhookUrl) async {
    final payload = {
      'text': message,
      if (inChannel != null) 'channel': inChannel!,
    };

    final request = await HttpClient().postUrl(Uri.parse(webhookUrl));
    final payloadData = utf8.encode(json.encode(payload));
    request.add(payloadData);
    final response = await request.close();
    return response.statusCode == 200;
  }
}

const webhookUrl =
    '<enter your webhook url>';
void testSend(String? newMessage) async {
  String defaultMessage = 'Hi there! I am dart';

  final message = SlackMessage(
      inChannel: '#software-development',
      message: newMessage ?? defaultMessage);
  if (await message.send(webhookUrl)) {
    print('Message sent successfully');
  } else {
    print('Message not sent');
  }
}

void main() {
  stdout.write("Enter your message : ");
  final message = stdin.readLineSync();
  testSend(message);
}