Todo App Backend Template
Flutter — Schema, API & AI Guide

Key Takeaways

Overview

A Todo app is one of the most common starting points for learning backend development. Under the hood it needs user registration, task CRUD, ownership-based access control, and optionally real-time sync.

The schema below defines two classes — _User (built-in) and Todo — connected by a Pointer. With the Back4app Flutter SDK, you can interact with this backend from your app — querying, creating, updating, and deleting objects — without writing a custom API layer.

Why Build Your Flutter Todo Backend with Back4app?

Back4app gives you a ready backend and a typed SDK so you can build your Todo app without writing REST glue or managing auth yourself.

• •SDK & type safety: The SDK keeps Todo and User type-safe and handles JSON so you write less boilerplate.
• •Async & optional offline: Use async/await; supported SDKs offer local pinning so your list can work offline and sync when back online.
• •Live Queries: Subscribe to Todo changes so the UI updates in real time over WebSockets.

Same schema and APIs for every stack — switch clients later without changing the backend.

Core Benefits

A production-ready Todo backend so you can ship faster and focus on your app.

Technical Stack

Everything powering this Todo app template at a glance.

ER Diagram

Entity-Relationship diagram for the Flutter Todo app data model.

erDiagram
    _User {
        String objectId PK
        String username
        String email
        String password
        Date createdAt
        Date updatedAt
    }

    Todo {
        String objectId PK
        String title
        Boolean done
        Date dueDate
        Number priority
        Pointer owner FK
        Date createdAt
        Date updatedAt
    }

    _User ||--o{ Todo : "owns"

Integration Flow

Auth-to-CRUD sequence: how your Flutter app talks to Back4app — login, then query and create todos.

sequenceDiagram
  participant User
  participant App as Flutter App
  participant Back4app as Back4app Cloud

  User->>App: Login
  App->>Back4app: Parse().login(username, password)
  Back4app-->>App: Session token
  App-->>User: Logged in

  User->>App: Load todos
  App->>Back4app: Query<Todo>().find()
  Back4app-->>App: List<Todo>
  App-->>User: Show list

  User->>App: Create todo
  App->>Back4app: todo.save()
  Back4app-->>App: Todo (objectId)
  App-->>User: Updated list

Data Dictionary

Complete field reference for every class in the schema.

Security & Permissions

How ownership, ACLs, and class-level permissions protect data in this schema.

Schema (JSON)

Raw JSON schema definition — copy and use in your Back4app app or import via the API.

{
  "classes": [
    {
      "className": "Todo",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "title": {
          "type": "String",
          "required": true
        },
        "done": {
          "type": "Boolean",
          "required": false,
          "defaultValue": false
        },
        "dueDate": {
          "type": "Date",
          "required": false
        },
        "priority": {
          "type": "Number",
          "required": false,
          "defaultValue": 3
        },
        "owner": {
          "type": "Pointer",
          "targetClass": "_User",
          "required": false
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    },
    {
      "className": "_User",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "username": {
          "type": "String",
          "required": true
        },
        "email": {
          "type": "String",
          "required": true
        },
        "password": {
          "type": "String",
          "required": true
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    }
  ]
}

API Playground

Try the REST and GraphQL endpoints for the Todo schema. Responses from the example data above — no Back4app account needed.

Uses the same Todo schema as this template.

Step-by-Step Flutter Integration

Connect to your Back4app backend from a Flutter app using the Back4app Flutter SDK.

1. Step 1: Install Back4app Flutter SDK

   Add the Back4app SDK for your stack (e.g. npm, pubspec, or package manager).

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   dependencies:
     flutter:
       sdk: flutter
     parse_server_sdk_flutter: ^7.0.0

2. Step 2: Initialize Back4app in your app

   Initialize the Back4app SDK at app startup with your App ID and server URL.

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   import 'package:parse_server_sdk_flutter/parse_server_sdk_flutter.dart';
   
   void main() async {
     WidgetsFlutterBinding.ensureInitialized();
   
     await Parse().initialize(
       'YOUR_APP_ID',
       'https://parseapi.back4app.com',
       clientKey: 'YOUR_CLIENT_KEY',
       autoSendSessionId: true,
     );
   
     runApp(const MyApp());
   }

3. Step 3: Query all todos

   Use the SDK to fetch all Todo objects, sorted by priority.

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   Future<List<ParseObject>> getTodos() async {
     final query = QueryBuilder<ParseObject>(ParseObject('Todo'))
       ..orderByAscending('priority');
   
     final response = await query.query();
   
     if (response.success && response.results != null) {
       return response.results as List<ParseObject>;
     }
     return [];
   }

4. Step 4: Create a todo

   Create a new Todo with title, done, and priority, then save.

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   Future<void> createTodo(String title, {int priority = 3}) async {
     final todo = ParseObject('Todo')
       ..set('title', title)
       ..set('done', false)
       ..set('priority', priority);
   
     final response = await todo.save();
   
     if (response.success) {
       print('Todo created: ${response.result.objectId}');
     }
   }

5. Step 5: Update and delete todos

   Update fields and save, or delete the object.

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   // Mark a todo as done
   Future<void> markDone(String objectId) async {
     final todo = ParseObject('Todo')
       ..objectId = objectId
       ..set('done', true);
   
     await todo.save();
   }
   
   // Delete a todo
   Future<void> deleteTodo(String objectId) async {
     final todo = ParseObject('Todo')..objectId = objectId;
     await todo.delete();
   }

Full Data Model

Copy a complete Todo model for type-safe serialization (e.g. class, interface, or type definition).

class Todo {
  final String? objectId;
  final String title;
  final bool done;
  final DateTime? dueDate;
  final int priority;
  final String? ownerId;
  final DateTime? createdAt;
  final DateTime? updatedAt;

  Todo({
    this.objectId,
    required this.title,
    this.done = false,
    this.dueDate,
    this.priority = 3,
    this.ownerId,
    this.createdAt,
    this.updatedAt,
  });

  factory Todo.fromJson(Map<String, dynamic> json) {
    return Todo(
      objectId: json['objectId'] as String?,
      title: json['title'] as String,
      done: json['done'] as bool? ?? false,
      dueDate: json['dueDate'] != null ? DateTime.parse(json['dueDate']) : null,
      priority: json['priority'] as int? ?? 3,
      ownerId: json['owner'] is Map ? (json['owner'] as Map)['objectId'] as String? : null,
      createdAt: json['createdAt'] != null ? DateTime.parse(json['createdAt']) : null,
      updatedAt: json['updatedAt'] != null ? DateTime.parse(json['updatedAt']) : null,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      if (objectId != null) 'objectId': objectId,
      'title': title,
      'done': done,
      if (dueDate != null) 'dueDate': dueDate!.toIso8601String(),
      'priority': priority,
      if (ownerId != null) 'owner': {'__type': 'Pointer', 'className': '_User', 'objectId': ownerId},
      if (createdAt != null) 'createdAt': createdAt!.toIso8601String(),
      if (updatedAt != null) 'updatedAt': updatedAt!.toIso8601String(),
    };
  }
}

Frequently Asked Questions

Common questions about the Todo app backend template.