Importing Dart Libraries

Importing Dart Libraries

About

• Code Reuse: Share functionality across files
• Core Libraries: Built-in Dart libraries
• Third-party: External package imports
• Organization: Logical code separation

Main Topics

1. Basic Import

   • Definition: import keyword
   • Example:

     import 'dart:math'; // Core library
     import 'package:flutter/material.dart'; // Package
     import 'lib/utils.dart'; // Local file

2. Core Libraries

   • Definition: Dart SDK provided
   • Example:

     import 'dart:async'; // Async operations
     import 'dart:convert'; // JSON handling

3. Package Imports

   • Definition: From pub.dev
   • Example:

     import 'package:http/http.dart';
     import 'package:provider/provider.dart';

4. Relative Imports

   • Definition: Project file paths
   • Example:

     import '../widgets/header.dart';
     import './constants.dart';

5. Initialization

   • Definition: deferred as

   • Example:

     import 'package:heavy_library/heavy.dart' deferred as heavy;
     
     void load() async {
       await heavy.loadLibrary();
       heavy.run();
     }

How to Use

• Core: Start with dart: libraries
• Packages: Add to pubspec first
• Organization: Group related imports
• Performance: Defer heavy libraries

How It Works

1. Resolution: Path or package lookup
2. Loading: At runtime
3. Scope: Brings identifiers into namespace
4. Caching: Single library instance

Example:

// Typical Flutter app imports
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'dart:async';

// Local imports
import '../models/user.dart';
import './api_service.dart';

Conclusion

Importing libraries in Dart provides access to core functionality, third-party packages, and your own organized code. Proper import practices keep your codebase clean and maintainable while enabling powerful code reuse across projects.