Todo App Backend Template
iOS — 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 iOS 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 iOS Todo Backend with Back4app?

Back4app gives iOS apps a Swift-friendly SDK and offline support so you can ship a polished Todo app quickly.

• •Swift and Codable: Use the Parse iOS SDK with async/await and Codable; type-safe models and clean serialization.
• •Offline and sync: Pin Todo objects locally; query from the local datastore when offline and sync when connected.
• •Live Queries: Subscribe to Todo changes for real-time updates in your SwiftUI or UIKit UI.

Ideal for iOS developers using Swift and value types.

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 iOS 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 iOS app talks to Back4app — login, then query and create todos.

sequenceDiagram
  participant User
  participant App as iOS App
  participant Back4app as Back4app Cloud

  User->>App: Login
  App->>Back4app: ParseUser.logIn(username:password:)
  Back4app-->>App: Session token
  App-->>User: Logged in

  User->>App: Load todos
  App->>Back4app: ParseQuery.find()
  Back4app-->>App: [PFObject]
  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 iOS Integration

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

1. Step 1: Install Back4app iOS SDK

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

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   // Package.swift or CocoaPods
   // SPM: .package(url: "https://github.com/parse-community/Parse-Swift", from: "4.0.0")
   // Podfile: pod 'Parse'

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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   Parse.initialize(
       configuration: ParseClientConfiguration {
           $0.applicationId = "YOUR_APP_ID"
           $0.clientKey = "YOUR_CLIENT_KEY"
           $0.server = "https://parseapi.back4app.com/"
       }
   )

3. Step 3: Query all todos

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

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   func getTodos() async throws -> [PFObject] {
       let query = PFQuery(className: "Todo")
       query.order(byAscending: "priority")
       return try await query.findObjects()
   }

4. Step 4: Create a todo

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

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   func createTodo(title: String, priority: Int = 3) async throws {
       let todo = PFObject(className: "Todo")
       todo["title"] = title
       todo["done"] = false
       todo["priority"] = priority
       try await todo.save()
   }

5. Step 5: Update and delete todos

   Update fields and save, or delete the object.

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   // Mark done
   func markDone(objectId: String) async throws {
       let query = PFQuery(className: "Todo")
       let todo = try await query.getObjectWithId(objectId)
       todo["done"] = true
       try await todo.save()
   }
   
   // Delete
   func deleteTodo(objectId: String) async throws {
       let query = PFQuery(className: "Todo")
       let todo = try await query.getObjectWithId(objectId)
       try await todo.delete()
   }

Full Data Model

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

// Todo.swift — matches Back4app schema
struct Todo: Codable {
    var objectId: String?
    var title: String
    var done: Bool
    var dueDate: Date?
    var priority: Int
    var owner: Pointer<_User>?
    var createdAt: Date?
    var updatedAt: Date?
}

func toTodo(_ obj: PFObject) -> Todo {
    Todo(
        objectId: obj.objectId,
        title: obj["title"] as? String ?? "",
        done: obj["done"] as? Bool ?? false,
        dueDate: obj["dueDate"] as? Date,
        priority: obj["priority"] as? Int ?? 3,
        owner: obj["owner"] as? Pointer<_User>,
        createdAt: obj.createdAt,
        updatedAt: obj.updatedAt
    )
}

Frequently Asked Questions

Common questions about the Todo app backend template.