[Rust] How do I create, fund, and transfer from a new purse?

Creating, funding, and transferring from a new purse can be done in just a few lines of code. Using the Rust crate, the below walk-through explains each part of the purse creation process, including deploying and calling the contract on-chain.

1. Create a purse:

This step created a new purse under the account context

let second_purse = system::create_purse();

2. Fund purse

This step transfers the amount from the account's main purse to the newly created purse.

let source: URef = account::get_main_purse();
...
system::transfer_from_purse_to_purse(source, second_purse, amount, None).unwrap_or_revert();

3. Store purse into contract named_keys

This step stores the newly created purse into the contract's named_keys

let mut named_keys: BTreeMap<String, Key> = BTreeMap::new();

//store purse into contract's named_keys
named_keys.insert(String::from("second_purse"), second_purse.into());

4. Entry point

• get the target account hash

let account_hash_key: Key = runtime::get_named_arg("account_hash");
 let target_account_hash = account_hash_key.into_account().unwrap();

• transfer amount from created purse to target public key

system::transfer_from_purse_to_account(source_purse, target_account_hash, amount, None)
     .unwrap_or_revert();

Command-line instructions

1. Install the contract

casper-client put-deploy \
--chain-name casper-test \
--node-address http://<NODE_ADDRESS_HERE>:7777 \
--payment-amount 20000000000 \
--session-path <PATH_TO>/target/wasm32-unknown-unknown/release/contract.wasm \
--session-arg "amount:U512='9000000000'" \
--secret-key <PATH_TO>/secret_key.pem 

2. Call entry point "transfer_amount"

casper-client put-deploy --chain-name casper-test \
--node-address http://94.130.10.55:7777 \
--secret-key <PATH_TO>/secret_key.pem \
--session-hash "hash-4f3de8e812f8bfee3e088461b325b5136d69307fc62aafa034298e16b818e332" \
--session-entry-point "transfer_amount"  \
--session-arg "account_hash:key='account-hash-d9758b25962f4cba82ba0047389af97a70acb7df43b391f9ffb293801bea5061'" \
--payment-amount 3000000000

The full body of code to initialize, fund, and set up an entry point looks like:

#![no_std]
#![no_main]

extern crate alloc;

use alloc::{collections::BTreeMap, string::String, vec};
use casper_contract::{
    contract_api::{account, runtime, storage, system},
    unwrap_or_revert::UnwrapOrRevert,
};
use casper_types::{
    CLType, EntryPoint, EntryPointAccess, EntryPointType, EntryPoints, Key, URef, U512,
};

#[no_mangle]
pub fn transfer_amount() {
    let source_purse = runtime::get_key("second_purse")
        .unwrap()
        .into_uref()
        .unwrap();

    let account_hash_key: Key = runtime::get_named_arg("account_hash");
    let target_account_hash = account_hash_key.into_account().unwrap();
    let amount = U512::from(1000000000);

    system::transfer_from_purse_to_account(source_purse, target_account_hash, amount, None)
        .unwrap_or_revert();
}

#[no_mangle]
pub extern "C" fn call() {
    let amount: U512 = runtime::get_named_arg("amount");
    let source: URef = account::get_main_purse();

    //create purse
    let second_purse = system::create_purse();

    //fund purse
    system::transfer_from_purse_to_purse(source, second_purse, amount, None).unwrap_or_revert();

    let mut named_keys: BTreeMap<String, Key> = BTreeMap::new();

    //store purse into contract's named_keys
    named_keys.insert(String::from("second_purse"), second_purse.into());

    // Create entry point
    let mut entry_points = EntryPoints::new();
    entry_points.add_entry_point(EntryPoint::new(
        "transfer_amount",
        vec![],
        CLType::Unit,
        EntryPointAccess::Public,
        EntryPointType::Contract,
    ));

    let (stored_contract_hash, _) =
        storage::new_locked_contract(entry_points, Some(named_keys), None, None);
    runtime::put_key("transfer_contract", stored_contract_hash.into());
}

If you have any concerns, questions, or issues, please submit a request to our support team here:

https://support.casperlabs.io/hc/en-gb/requests/new