data_inmemory

An in-memory implementation of the DataClient interface, designed primarily for testing, local development, or scenarios where a lightweight, non-persistent data store is sufficient. This package is part of the Flutter News App - Full Source Code Toolkit.

Description

DataInMemory provides a way to simulate a backend data source entirely in memory. It supports:

• Standard CRUD (Create, Read, Update, Delete) operations.
• User-scoped data: Operations can be tied to a specific userId.
• Global data: Operations can target data not associated with any user.
• Rich, document-style querying via the readAll method's filter parameter.
• General Filtering: Supports operators like $in, $nin, $ne, $gte, etc., on any field, including nested ones (category.id).
• Simulated Full-Text Search: Accepts a special q key in the filter ({'q': 'search term'}) to perform a case-insensitive substring search on the primary text field of a model (title for headlines, name for topics/sources).
• Multi-field sorting via a list of SortOption objects.
• Cursor-based pagination via the PaginationOptions object.

This client is useful for:

• Unit and integration testing of repositories or BLoCs that depend on DataClient.
• Rapid prototyping and local development without needing a live backend.
• Demonstrations or examples.

Getting Started

This package is typically used as a development dependency or a direct dependency in projects that require an in-memory data store for local or test environments.

To use this package, add data_inmemory to your pubspec.yaml dependencies.

dependencies:
  # data_client is also required as it defines the interface
  data_client:
    git:
      url: https://github.com/flutter-news-app-full-source-code/data-client.git
      # ref: <specific_commit_or_tag> # Optional: pin to a version
  data_inmemory:
    git:
      url: https://github.com/flutter-news-app-full-source-code/data-inmemory.git
      # ref: <specific_commit_or_tag> # Optional: pin to a version
  # core is needed for models and exceptions
  core:
    git:
      url: https://github.com/flutter-news-app-full-source-code/core.git
      # ref: <specific_commit_or_tag> # Optional: pin to a version

Then run dart pub get or flutter pub get.

Features

• Implements the DataClient<T> interface from package:data_client.
• In-memory storage for generic data types T.
• Support for initialData to pre-populate the client.
• User-scoped and global data operations.
• create, read, update, delete methods.
• A unified readAll method with support for rich filtering, multi-field sorting, and cursor-based pagination.
• Throws standard exceptions from package:core (e.g., NotFoundException, BadRequestException).
• count method for efficient document counting without fetching data.
• aggregate method to simulate basic MongoDB aggregation pipelines (supports $match, $group, $sort, $limit), enabling testing of analytics-style queries.

Usage

Here's a basic example of how to use DataInMemoryClient with a simple Article model:

import 'package:data_client/data_client.dart'; // Defines DataClient
import 'package:data_inmemory/data_inmemory.dart';
import 'package:core/core.dart'; // Assuming SuccessApiResponse etc. are here

// 1. Define your model (ensure it has an ID and toJson method)
class Article {
  Article({required this.id, required this.title, this.content});
  final String id;
  final String title; 
  final String? content;

  // Required for DataInMemoryClient
  Map<String, dynamic> toJson() => {
        'id': id,
        'title': title,
        // Add other fields for querying
        if (content != null) 'content': content,
      };
  
  // For easy comparison in examples/tests
  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Article &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          title == other.title &&
          content == other.content;

  @override
  int get hashCode => id.hashCode ^ title.hashCode ^ content.hashCode;
}

void main() async {
  // 2. Define helper functions for the client
  String getArticleId(Article article) => article.id;
  Map<String, dynamic> articleToJson(Article article) => article.toJson();

  // 3. Instantiate the client
  final client = DataInMemoryClient<Article>(
    getId: getArticleId,
    toJson: articleToJson,
    initialData: [
      Article(id: 'article1', title: 'First Article', content: 'Hello world!'),
    ],
  );

  // 4. Use the client
  try {
    // Create a new article
    final newArticle = Article(id: 'article2', title: 'Second Article');
    SuccessApiResponse<Article> createResponse =
        await client.create(item: newArticle);
    print('Created: ${createResponse.data.title}');

    // Read an article
    SuccessApiResponse<Article> readResponse =
        await client.read(id: 'article1');
    print('Read: ${readResponse.data.title}');

    // Query articles with a search term and other filters
    final filter = {
      'q': 'article', // Search for 'article' in title
      'content': {'\$ne': null} // And content is not null
    };
    final sort = [const SortOption('title', SortOrder.desc)];
    final pagination = const PaginationOptions(limit: 5);

    final queryResponse = await client.readAll(
      filter: filter,
      sort: sort,
      pagination: pagination,
    );

    print('Found ${queryResponse.data.items.length} sorted articles matching query:');
    for (final article in queryResponse.data.items) {
      print('- ${article.title}');
    }
    print('Has more pages: ${queryResponse.data.hasMore}');

    // Count published articles
    final countResponse = await client.count(filter: {'isPublished': true});
    print('Number of published articles: ${countResponse.data}');

    // Run an aggregation pipeline to get article count per category
    final aggregateResponse = await client.aggregate(
      pipeline: [
        {
          r'$group': {
            '_id': r'$category.name',
            'count': {r'$sum': 1},
          },
        },
        {
          r'$sort': {'count': -1},
        },
      ],
    );
    print('Article count per category:');
    for (final result in aggregateResponse.data) {
      print('- ${result['_id']}: ${result['count']}');
    }

  } on HtHttpException catch (e) {
    print('An error occurred: ${e.message}');
  }
}

🔑 Licensing

This package is source-available and licensed under the PolyForm Free Trial 1.0.0. Please review the terms before use.

For commercial licensing options that grant the right to build and distribute unlimited applications, please visit the main Flutter News App - Full Source Code Toolkit organization.