deposit

A data backend agnostic repository pattern package for Dart and Flutter.

Test style: very good analysis license: MIT

Overview

The goal of this package is to provide a repository pattern that is agnostic for any given data backend.

This design pattern (which comes from Domain-driven Design) helps to write data layers without having to know the data backend. This package abstracts all the aspects of the pattern into a single consistent API.

Entity

An Entity class is the base of the data model part of the repository pattern. The class defines how data from a backend should be read and it serves as a reference to that data on the backend.

Defining an Entity

class MovieEntity extends Entity {
  MovieEntity({
    this.id,
    required this.title,
  });

  factory MovieEntity.fromJSON(Map<String, dynamic> data) {
    return MovieEntity(
      id: data['id'] as int?,
      title: data['title'] as String? ?? 'No title',
    );
  }

  int? id;

  String title;

  @override
  Map<String, dynamic> toJSON() {
    return <String, dynamic>{
      'id': id,
      'title': title,
    };
  }

  @override
  String toString() => 'Movie(id: $id, title: $title)';
}

Deposit

A Deposit is a class that provides a single consistent API for the repository pattern. It uses an Entity as a relation on how to read and write data to any given data backend.

A Deposit class has a reference to table/collection on the data backend from which it can read and write data.

Creating a Deposit

You can create a Deposit in two different ways. The first one is by extending from the class itself, this allows for adding custom methods tailed to any specific usecase:

class MovieDeposit extends Deposit<MovieEntity, int> {
  MovieDeposit() : super('movies', MovieEntity.fromJSON, adapter: OptionalDepositAdapter());
}

The Deposit class can also be used directly, while this is not recommend there is also nothing against it:

final movieDeposit = Deposit<MovieEntity, int>('movies', MovieEntity.fromJSON);

DepositAdapter

The DepositAdapter is an agnostic class that defines how a Deposit instance should talk to a data backend. By default a Deposit instance will use the Deposit.defaultAdapter if no adapter was passed on initialization.

The deposit package comes with an in-memory adapter called MemoryDepositAdapter. But there is by default no adapter set, this should be done explicitly by the package user.

The following data backends are officially supported:

Setting the default adapter

By setting the Deposit.defaultAdapter any Deposit instance that did not receive an adapter on initialization will use the default adapter:

Deposit.defaultAdapter = MemoryDepositAdapter();

Libraries

deposit