firestore_paging_controller 0.1.0

Lazily load and display pages of items as the user scrolls down your screen, using Firestore with some enhancements.

Firestore Paging Controller

This is a simple Firestore Paging Controller package build on top of the infinite_scroll_pagination package. It provides a simple way to paginate through Firestore collections.

Additionally, it provides a simple way to merge multiple queries into a single stream, which ultimately allows you to have an OR query. On top of that, it also allows ordering the results of the merged queries, which is not possible with Firestore. Internally, it uses the buffer to make sure it doesn't show the items in the wrong order.

Getting Started

To use this package, you need to add the following dependency in your pubspec.yaml file:

dependencies:
  firestore_paging_controller: any

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Usage

To use this package, you need to create a FirestorePagingController and (optionally) pass it the queries you want to paginate through. Here is an example:

import 'package:firestore_paging_controller/firestore_paging_controller.dart';

final controller = FirestorePagingController.withoutType(
  basePath: 'posts',
  queryBuilders: [
    (query) => query.where('creatorId', isEqualTo: userId),
    (query) => query.where('taggedUserId', isEqualTo: userId),
  ],
  orderBy: 'createdAt',
  orderByDescending: true,
  pageSize: 10,
);

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This will create a controller that will paginate through the items that have the creatorId or taggedUserId equal to the userId. The controller will fetch 10 items per page for each query.

After creating the controller, you can use it in a widget from the infinite_scroll_pagination package. Here is an example:

PagedListView(
  pagingController: controller,
  builderDelegate: PagedChildBuilderDelegate<QueryDocumentSnapshot<Map<String, dynamic>>>(
    itemBuilder: (context, snapshot, index) => Post(snapshot.data()),
  ),
);

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If you want to use the type-safe version of the controller, you can do the following:

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firestore_paging_controller/firestore_paging_controller.dart';

final controller = FirestorePagingController<PostModel>.converted(
  basePath: 'posts',
  queryBuilders: [
    (query) => query.where('creatorId', isEqualTo: userId),
    (query) => query.where('taggedUserId', isEqualTo: userId),
  ],
  orderBy: 'createdAt',
  orderByDescending: true,
  pageSize: 10,
  fromMap: (data) => PostModel.fromMap(data),
);

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Then it can be used like this:

PagedListView<int, QueryDocumentSnapshot<T>>(
  pagingController: controller,
  builderDelegate: PagedChildBuilderDelegate<QueryDocumentSnapshot<T>>(
    itemBuilder: (context, snapshot, index) => Post(snapshot.data()),
  ),
);

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Reminders:

• The queries you pass to the controller should not have any limit or orderBy applied to them.
• You may need to create an index in Firestore for the queries you are using in the controller. Look at the logs for the error message and create the index accordingly.