class CacheUtil { static final CacheUtil _instance = CacheUtil._internal(); static final Map _cache = {}; CacheUtil._internal(); factory CacheUtil() => _instance; static CacheUtil get instance => _instance; void set(String key, dynamic value) { _cache[key] = value; } dynamic get(String key) { return _cache[key]; } bool containsKey(String key) { return _cache.containsKey(key); } dynamic getOrElse(String key, dynamic fallback) { return _cache.containsKey(key) ? _cache[key] : fallback; } void delete(String key) { _cache.remove(key); } void clear() { _cache.clear(); } }