Dart Developer Library

Developer Tools

log('Debug message', 
    name: 'MyApp', 
    level: Level.INFO);

debugger(when: condition);
inspect(myObject);

Timeline.startSync('operation');
// code here
Timeline.finishSync();

var counter = Counter('requests');
counter.value++;

🔹 Logging and Debugging

Use structured logging for better debugging:

import 'dart:developer';

void main() {
  // Basic logging
  log('Application starting...');
  
  // Logging with categories and levels
  log('User login attempt', 
      name: 'Auth', 
      level: Level.INFO);
  
  log('Database connection failed', 
      name: 'Database', 
      level: Level.SEVERE,
      error: 'Connection timeout');
  
  // Conditional debugging
  var isDebugMode = true;
  debugger(when: isDebugMode);
  
  // Inspect objects
  var user = {'name': 'John', 'age': 30};
  inspect(user);
  
  // Log with additional data
  log('Processing order',
      name: 'OrderService',
      level: Level.INFO,
      time: DateTime.now(),
      sequenceNumber: 1001);
}

🔹 Performance Profiling

Measure and analyze application performance:

import 'dart:developer';

void main() async {
  // Time a synchronous operation
  Timeline.startSync('data-processing');
  processData();
  Timeline.finishSync();
  
  // Time an asynchronous operation
  Timeline.timeSync('database-query', () {
    return queryDatabase();
  });
  
  // Manual timing with flow events
  var flowId = Flow.begin();
  Timeline.startSync('step-1');
  await step1();
  Timeline.finishSync();
  
  Timeline.startSync('step-2');
  await step2();
  Timeline.finishSync();
  Flow.end(flowId);
  
  // Custom performance counters
  var requestCounter = Counter('http_requests', 'Number of HTTP requests');
  requestCounter.value = 150;
  
  var responseTime = Gauge('response_time_ms', 'Average response time');
  responseTime.value = 45.2;
}

void processData() {
  // Simulate data processing
  for (int i = 0; i < 1000000; i++) {
    // Processing logic
  }
}

Future<void> queryDatabase() async {
  await Future.delayed(Duration(milliseconds: 100));
}

Future<void> step1() async {
  await Future.delayed(Duration(milliseconds: 50));
}

Future<void> step2() async {
  await Future.delayed(Duration(milliseconds: 30));
}

🔹 Service Extensions

Create custom debugging tools and extensions:

import 'dart:developer';
import 'dart:convert';

void main() {
  // Register a custom service extension
  registerExtension('ext.myapp.getStats', (method, parameters) async {
    var stats = {
      'uptime': DateTime.now().millisecondsSinceEpoch,
      'memory_usage': '45MB',
      'active_users': 127,
      'requests_per_second': 23.5
    };
    
    return ServiceExtensionResponse.result(jsonEncode(stats));
  });
  
  // Register a service to toggle debug mode
  var debugMode = false;
  registerExtension('ext.myapp.toggleDebug', (method, parameters) async {
    debugMode = !debugMode;
    log('Debug mode: ${debugMode ? 'ON' : 'OFF'}', name: 'DebugToggle');
    
    return ServiceExtensionResponse.result(jsonEncode({
      'debug_mode': debugMode
    }));
  });
  
  // Register a service to clear cache
  registerExtension('ext.myapp.clearCache', (method, parameters) async {
    // Simulate cache clearing
    await Future.delayed(Duration(milliseconds: 100));
    log('Cache cleared successfully', name: 'CacheManager');
    
    return ServiceExtensionResponse.result(jsonEncode({
      'status': 'success',
      'message': 'Cache cleared'
    }));
  });
  
  log('Service extensions registered', name: 'ServiceManager');
}