š Project: GitHub API Client
š Lesson 11: Fetch Live Data
ā± 35-40 min
š Advanced
šÆ Objective
Build a simulated GitHub API client that fetches user profiles and repositories. Practice HTTP requests, JSON parsing, error handling, and concurrent API calls.
Requirements
- Create a
GitHubClientclass with methods for user and repo data - Simulate API calls with realistic delays and responses
- Fetch multiple users concurrently
- Handle API errors (404, 403 rate limit, 500)
- Display formatted user profiles and repository lists
import 'dart:async';
import 'dart:convert';
import 'dart:math';
// Step 1: Data models
class GitHubUser {
final String login;
final String name;
final String? bio;
final int publicRepos;
final int followers;
final String avatarUrl;
GitHubUser({
required this.login,
required this.name,
this.bio,
required this.publicRepos,
required this.followers,
required this.avatarUrl,
});
factory GitHubUser.fromJson(Map json) {
return GitHubUser(
login: json['login'] as String,
name: json['name'] as String? ?? json['login'] as String,
bio: json['bio'] as String?,
publicRepos: json['public_repos'] as int? ?? 0,
followers: json['followers'] as int? ?? 0,
avatarUrl: json['avatar_url'] as String? ?? '',
);
}
}
class GitHubRepo {
final String name;
final String? description;
final String language;
final int stars;
final int forks;
GitHubRepo({
required this.name,
this.description,
this.language = 'Unknown',
required this.stars,
required this.forks,
});
factory GitHubRepo.fromJson(Map json) {
return GitHubRepo(
name: json['name'] as String,
description: json['description'] as String?,
language: json['language'] as String? ?? 'Unknown',
stars: json['stargazers_count'] as int? ?? 0,
forks: json['forks_count'] as int? ?? 0,
);
}
}
// Step 2: Custom exceptions
class GitHubApiException implements Exception {
final int statusCode;
final String message;
GitHubApiException(this.statusCode, this.message);
@override
String toString() => 'GitHub API Error ($statusCode): $message';
}
class RateLimitException extends GitHubApiException {
RateLimitException() : super(403, 'API rate limit exceeded');
}
class UserNotFoundException extends GitHubApiException {
UserNotFoundException(String username) : super(404, 'User not found: $username');
}
// Step 3: Simulated GitHub client
class GitHubClient {
static const String _baseUrl = 'https://api.github.com';
final Random _random = Random();
int _requestCount = 0;
Future> _simulateRequest(String endpoint) async {
_requestCount++;
// Simulate network delay
int delayMs = 300 + _random.nextInt(700);
await Future.delayed(Duration(milliseconds: delayMs));
// Simulate rate limiting after 10 requests
if (_requestCount > 10) {
throw RateLimitException();
}
// Simulate occasional server error
if (_random.nextInt(20) == 0) {
throw GitHubApiException(500, 'Internal server error');
}
// Return simulated data based on endpoint
if (endpoint.contains('/users/')) {
return _generateUserData(endpoint);
} else if (endpoint.contains('/repos')) {
return _generateRepoData();
}
throw GitHubApiException(400, 'Bad request');
}
Map _generateUserData(String endpoint) {
final username = endpoint.split('/').last;
return {
'login': username,
'name': '${username[0].toUpperCase()}${username.substring(1)}',
'bio': 'Dart developer passionate about clean code',
'public_repos': 10 + _random.nextInt(50),
'followers': 50 + _random.nextInt(200),
'avatar_url': 'https://avatars.githubusercontent.com/$username',
};
}
Map _generateRepoData() {
final languages = ['Dart', 'JavaScript', 'Python', 'TypeScript', 'Go'];
final names = ['awesome-project', 'cli-tool', 'web-app', 'dart-package', 'flutter-ui'];
return {
'name': names[_random.nextInt(names.length)],
'description': 'An awesome project built with Dart',
'language': languages[_random.nextInt(languages.length)],
'stargazers_count': _random.nextInt(1000),
'forks_count': _random.nextInt(200),
};
}
Future getUser(String username) async {
try {
final data = await _simulateRequest('/users/$username');
return GitHubUser.fromJson(data);
} on GitHubApiException {
rethrow;
}
}
Future> getUserRepos(String username) async {
try {
final repoCount = 3 + _random.nextInt(5);
final repos = [];
for (int i = 0; i < repoCount; i++) {
final data = await _simulateRequest('/users/$username/repos');
repos.add(GitHubRepo.fromJson(data));
}
return repos;
} on GitHubApiException {
rethrow;
}
}
Future> getMultipleUsers(List usernames) async {
final futures = usernames.map((username) =>
getUser(username).catchError((e) {
print('ā ļø Failed to fetch $username: $e');
return null;
})
);
final results = await Future.wait(futures);
return results.whereType().toList();
}
}
// Step 4: Display utilities
void displayUser(GitHubUser user) {
print('š¤ ${user.name} (@${user.login})');
if (user.bio != null) print(' š ${user.bio}');
print(' š¦ Repos: ${user.publicRepos} | š„ Followers: ${user.followers}');
}
void displayRepo(GitHubRepo repo) {
final starIcon = repo.stars > 100 ? 'ā' : 'ā';
print(' $starIcon ${repo.name} (${repo.language})');
if (repo.description != null) print(' ${repo.description}');
print(' ā
${repo.stars} | š“ ${repo.forks}');
}
// Step 5: Main program
Future main() async {
print('āāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāā');
print('ā GITHUB API CLIENT ā');
print('āāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāāā\n');
final client = GitHubClient();
// Fetch single user
print('š Fetching user: dart-dev...');
try {
final user = await client.getUser('dart-dev');
displayUser(user);
// Fetch repos
print('\nš¦ Fetching repositories...');
final repos = await client.getUserRepos('dart-dev');
for (var repo in repos) {
displayRepo(repo);
}
} on UserNotFoundException catch (e) {
print('ā $e');
} on RateLimitException catch (e) {
print('ā $e');
}
// Fetch multiple users
print('\nš„ Fetching multiple users concurrently...');
final usernames = ['flutter', 'dart-lang', 'google'];
final users = await client.getMultipleUsers(usernames);
print('\nš Results: ${users.length}/${usernames.length} users fetched');
for (var user in users) {
print('');
displayUser(user);
}
}