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Use Cases
User Storage

UserStorage Contract

The UserStorage contract sets up a scenario to store and retrieve string values associated with different user accounts. This contract demonstrates basic per-user data storage and retrieval functionality within a blockchain environment.

from backend.node.genvm.icontract import IContract
 
class UserStorage(IContract):
    def __init__(self):
        self.storage = {}
 
    def get_complete_storage(self) -> dict:
        return self.storage
 
    def get_account_storage(self, account_address: str) -> str:
        return self.storage[account_address]
 
    def update_storage(self, new_storage: str) -> None:
        self.storage[contract_runner.from_address] = new_storage

Code Explanation

  • Initialization: The UserStorage class initializes the contract with an empty dictionary self.storage to store user-specific data.
  • Read Methods:
    • get_complete_storage() returns the entire storage dictionary, containing all user data.
    • get_account_storage(account_address) returns the stored value for a specific user account.
  • Write Method: update_storage(new_storage) allows updating the stored value for the user who called the contract (identified by contract_runner.from_address).

Deploying the Contract

To deploy the UserStorage contract, you don't need to provide any initial parameters:

  1. Deploy the Contract: Simply deploy the contract to make it ready for interaction.

Checking the Contract State

After deploying the contract, its address is displayed and you can check its state in the Read Methods section.

  • Use get_complete_storage() to see all stored user data.
  • Use get_account_storage(account_address) to see the data for a specific user account.

Executing Transactions

To interact with the deployed contract, go to the Write Methods section. Here, you can call the update_storage method to change the stored value for the calling user. This triggers the contract's logic to update the storage with the new value.

Analyzing the Contract's Behavior

When the update_storage method is executed:

  • The contract updates the self.storage dictionary, associating the new value with the address of the user who called the function (contract_runner.from_address).
  • You can then use the get_account_storage() or get_complete_storage() methods to verify that the value has been updated for the specific user.

Handling Different Scenarios

  • Initial State: When the contract is first deployed, the storage is empty. get_complete_storage() will return an empty dictionary.
  • First Update for a User: When a user first calls update_storage, a new entry is created in the storage dictionary for that user's address.
  • Subsequent Updates: If a user calls update_storage again, their existing entry in the storage is updated with the new value.
  • Multiple Users: Different users can store and retrieve their own values independently.
  • Accessing Non-existent Data: If get_account_storage() is called with an address that hasn't stored any data yet, it will raise a KeyError.

You can view the logs to see detailed information about the contract interaction, including the values being stored and retrieved for different user accounts.

This UserStorage contract provides a simple example of how user-specific data can be stored and retrieved on a blockchain, demonstrating basic multi-user state management within a smart contract.

StorageERC-20 Token