Move Contract: tx::app

The Move contract tx::app provides a simple on-chain messaging service where users can sign and store messages. Each message is stored on the blockchain and associated with a timestamp and the sender's address. Here's a breakdown of the contract's key components:

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Constants and Structures:

• MODULE_ADMIN:

  • The address @tx is designated as the admin of the module. Only this admin can initialize the contract.

• EINVALID_ADMIN_ADDR:

  • An error code (1) representing an invalid admin address, used to ensure only the correct admin can initialize the contract.

• Txs (struct):

  • A data structure that stores a vector of signed messages (messages: vector<String>).

• NewTx (event):

  • An event structure with three fields:
    • timestamp: u64: The time the message was signed.
    • user: address: The address of the user who signed the message.
    • message: String: The content of the signed message.
  • The event is emitted every time a new message is signed.

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Entry Functions:

1. init(admin: &signer)

• Initializes the contract and can only be called by the admin (designated by @tx).
• Validates that the caller is the admin by checking if the caller's address matches MODULE_ADMIN.
• If valid, it creates a Txs struct with an empty list of messages and moves it under the admin's account.
• Error Handling: If the caller's address is not @tx, it aborts with the error EINVALID_ADMIN_ADDR.

2. sign_message(user: &signer, message: String)

• Allows any user to sign a message and store it in the Txs struct.
• The function:
  1. Adds the message to the messages vector in the Txs struct.
  2. Emits a NewTx event with the message, the sender's address, and the timestamp.
• This event helps track when and by whom messages are signed on the blockchain.

3. read_messages()

• A view-only function that retrieves all stored messages.
• Returns the list of messages stored in the Txs struct.
• This function does not modify the blockchain's state, making it safe for read-only operations.

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Interact with the contract

All the parameters and dependendecies are defined in Move.toml

1. Initial Setup** Initialize your Aptos CLI wallet and configure your environment.

aptos init

2. Check Account Information

aptos account list
aptos account balance

3. Compile Move Code

aptos move compile

4. Compile with Named Addresses

aptos move compile --named-addresses tx=<your_address>

5. Publish Your Contract On-Chain

aptos move publish --named-addresses tx=<your_address>

6. Initialize the Contract

aptos move run --function-id <module_address>::tx::app::init --profile default

7. Sign a Message

aptos move run --function-id <module_address>::tx::app::sign_message --profile default --args  <message>