ファクトリーパターンの違いに混乱 … Factory constructors class Logger { final String name; static final Map<String, Logger> _cache = <String, Logger>{}; Logger._internal(this.name); factory Logger(String name) { if (_cache.containsKey(name)) { return _cache[name]; } else { final logger = Logger._internal(name); _cache[name] = logger; return logger; } } }