Flutter shareable package of object-oriented classes

June 20, 2021 packages, Packages

json_cache

Json Cache is an object-oriented package to serve as a layer on top of local storage packages – packages that persist data locally on the user’s device -, unifying them as an elegant cache API.

In addition, this package gives the programmer great flexibility; it provides a set of classes that can be selected and combined in various ways to address specific caching requirements.

Why Json?

Because most of the local storage packages available for Flutter applications use json as the data format.
There is an one-to-one relationship between the Dart’s built-in type Map<String, dynamic> and json, which makes json encoding/decoding a trivial task.

Getting Started

JsonCache – the core interface of this package – represents the concept of cached data. It is defined as:

/// Represents a cached json data.
abstract class JsonCache {
  /// Frees up cache storage space.
  Future<void> clear();

  /// Refreshes some cached data by its associated key.
  Future<void> refresh(String key, Map<String, dynamic> data);

  /// Erases [key] and returns its associated data.
  Future<Map<String, dynamic>?> erase(String key);

  /// Recovers some cached data; null if a cache miss occurs - no [key] found.
  Future<Map<String, dynamic>?> recover(String key);
}

It’s reasonable to consider each cache entry (pair of key/data) as a group of related data. Thus, it is expected to cache user data in groups, in which a key represents the name of a single group of data. Example:

'profile': {'name': 'John Doe', 'email': 'johndoe@email.com', 'accountType': 'premium'};
'preferences': {'theme': {'dark': true}, 'notifications':{'enabled': true}}

Above the ‘profile’ key is associated with the group of profile related data; ‘preferences’, with preferences data.