Soroban Quest : Auth Store

Hi there! Welcome to my "Soroban Quest" blog post series. Soroban Quest is a gamified educational course where you’ll learn Soroban (new smart contract platform by Stellar Foundation) and earn badge rewards!. In this series, i will explain steps to complete every soroban quest and help you understand more about soroban smart contract itself.

We already completed the first quest in the previous post. The second quest is called "Auth Store". This quest will give you lesson how to store and retrieve data from contract storage using simple authentication.

Joining The Quest

To join the quest and get a Quest Account, use this command:

sq play 2

And dont forget to fund the quest account right away.

Examining README.md

After examining README.md, I found that the tasks for the 2nd quest is to:

• Build auth data store contract
• Deploy auth data store contract to the futurenet
• Invoke put function from the deployed contract to store some data
• Invoke get function from the deployed contract to retrieve that data

Lets read the contract code to get some more knowledge to do all that.

The Contract Code

#![no_std]
use error::ContractError;
use soroban_sdk::{bytes, contractimpl, panic_with_error, Address, Bytes, Env};

pub struct DataStoreContract;

#[contractimpl]
impl DataStoreContract {

    pub fn put(env: Env, user: Address, value: Bytes) -> Result<(), ContractError> {

        user.require_auth();
        if value.len() <= 10 {
            panic_with_error!(&env, ContractError::InputValueTooShort)
        }

that was passed,

        env.storage().set(&user, &value);

        Ok(()) // return ok if function call succeeded
    }

    pub fn get(env: Env, owner: Address) -> Bytes {
        env.storage()
            .get(&owner)
            .unwrap_or_else(|| Ok(bytes!(&env))) // This uses `unwrap_or_else` and closure which only evaluates Bytes(0) when necessary.
            .unwrap()
    }
}

mod error;
mod test;

The contract is located in lib.rs and contains two functions:

• put() - Stores data associated with an address if the address has authorized the write
• get() - Retrieves data associated with an address

The contract also includes an error module (error.rs) defining the ContractError type for error handling. The contract uses panic_with_error!() to panic with a custom ContractError if invalid input is provided to put(). This demonstrates panicking with a custom error type to provide more detailed error information.

put() function

Accepts an address (user), data (value - in hex)
Requires the address to have authorized the write by calling user.require_auth()
Checks that the data is at least 11 bytes long and panics if not
Stores the data associated with the address by calling env.storage().set()
Returns Ok if successful

This will store data to the storage based on specific address.

get() Function

• Accepts an address (owner) and contract environment (env) as parameters
• Retrieves the data associated with the address by calling env.storage().get()
• Returns the data or bytes of length 0 if no data is associated with the address

This allows retrieval of stored data associated with an address.

Building the Contract

To build the contract, use the following command:

cd 
cargo build --target wasm32-unknown-unknown --release

This should output a .wasm file in the ../target directory:

../target/wasm32-unknown-unknown/release/soroban_auth_store_contract.wasm

Deploying the Contract

To deploy the contract, use the following command:

soroban contract deploy --wasm /workspace/soroban-quest/target/wasm32-unknown-unknown/release/soroban_auth_store_contract.wasm

From this command you will get a Contract ID, save this for invoking it later.

Invoking the Contract

First we need to invoke put function to store data using this command format :

soroban contract invoke --id <AuthContractID> --fn put -- --user <QuestPublicKey> --value '<StoredDataInHex>'

Note : To convert string to hex use echo "YourString" | xxd -p
Next we will retrieve the stored data by invoking get function using this command :

soroban contract invoke --id <AuthContractID> -- get --owner <QuestPublicKey> 

By running that command you should get your stored data(in hex).

Checking the Quest

We already completed every step to complete the quest and this is the last thing you need to do. Check your quest and claim your badge reward. To check use the following command :

sq check 2

Congratulations! You have already completed 2 out of 6 quests. You have 4 more to go.