TheToDo Smart Contract

Overview

The TheToDo smart contract is a simple to-do list manager built on the Flow blockchain using Cadence. It allows users to create and manage their own to-do lists. Each user can create multiple to-do items, mark them as done, and retrieve their lists.

Contract Structure

1. Struct: List

• id: UInt32: A unique identifier for each to-do item.
• title: String: The title or description of the to-do item.
• is_done: Bool: A flag indicating whether the to-do item is completed.

The List struct is publicly accessible and has pub(set) access modifiers, allowing fields to be modified within the contract.

2. Variable: lists

• Type: {Address: {UInt32: List}}
• Description: A mapping that stores to-do lists for each user. The keys are user addresses, and the values are mappings of list IDs to List structs.

3. Initializer

• init(): Initializes the lists variable as an empty dictionary.

Functions

1. createList(owner: Address, title: String)

• Description: Creates a new to-do list item for the specified owner with the given title.
• Parameters:
  • owner: The address of the user creating the list.
  • title: The title of the new to-do item.
• Behavior:
  • Retrieves the existing to-do lists for the user or initializes a new one.
  • Generates a new ID based on the number of existing items.
  • Adds the new List to the user's list.

2. markListDone(owner: Address, id: UInt32)

• Description: Marks a specific to-do item as completed for the specified owner.
• Parameters:
  • owner: The address of the user who owns the list.
  • id: The ID of the to-do item to be marked as done.
• Behavior:
  • Retrieves the user's to-do list.
  • Marks the specified item as completed.

3. getListItem(owner: Address, id: UInt32): List?

• Description: Retrieves a specific to-do item from the user's list by its ID.
• Parameters:
  • owner: The address of the user who owns the list.
  • id: The ID of the to-do item to be retrieved.
• Returns: The List item if found, or nil if not.

4. getList(owner: Address): {UInt32: List}?

• Description: Retrieves all to-do items for the specified owner.
• Parameters:
  • owner: The address of the user whose list is to be retrieved.
• Returns: A dictionary of all List items for the user, or nil if no lists exist.

Usage Example

import TheToDo from 0x01

// Create a new to-do item
TheToDo.createList(owner: 0x01, title: "Finish Cadence tutorial")

// Mark the to-do item as done
TheToDo.markListDone(owner: 0x01, id: 1)

// Retrieve a specific to-do item
let item = TheToDo.getListItem(owner: 0x01, id: 1)

// Retrieve all to-do items for a user
let allItems = TheToDo.getList(owner: 0x01)