Sample Code for System Contract

System Contract

Using the VSYS Python API Wrapper pyvsystems

Install pyvsystems

pyvsystems can be installed by first cloning the github repository

git clone https://github.com/virtualeconomy/pyvsystems.git

Then using pip, we can install the repository as a package

pip3 install pyvsystems/.

Then we can simply import pyvsystems in your own workplace

 

Using the System Contract functions

The System Contract allows VSYS Coins to interact with Contract databases where it otherwise wouldn't be possible. The sysSend function is meant to allow for contract functions to be able to send VSYS coins, directly calling it would be no different from a regular payment transaction. The two primary functions of the System Contract is the sysDeposit and sysWithdraw functions, depositing and withdraw from VSYS contracts allowing them to control these funds.

Triggers	Inputs	Input Types	Description
N/A	N/A	N/A	N/A

Executable Functions	Function ID	Inputs	Input Types	Description
Send	0	("recipient", "amount")	(address, amount)	Send VSYS through the System contract
Deposit	1	("sender", "contract", "amount")	(address, contract_account, amount)	Deposit VSYS into other contracts
Withdraw	2	("contract", "recipient", "amount")	(contract_account, address, amount)	Withdraw VSYS from other contracts
Transfer	3	("sender", "recipient", "amount")	(address, address, amount)	Transfer VSYS from sender to recipient through the System contract

Importing pyvsystems and setting up initial variables

import pyvsystems as pv
from pyvsystems import Account
from pyvsystems.contract_helper import *

system_contract_helper = SystemContractHelper()

custom_wrapper = pv.create_api_wrapper("<your_node_address>", api_key="<your_node_api_key (optional)>")
# chain = pv.Chain(chain_name='mainnet', chain_id='M', address_version=5, api_wrapper=custom_wrapper)
chain = pv.Chain(chain_name='testnet', chain_id='T', address_version=5, api_wrapper=custom_wrapper)
sender = Account(chain=chain, seed="<your_sender_seed>")

Using a previously deployed payment channel contract id, I have executed the System Contract in order to deposit VSYS into the payment channel contract.

# sysDeposit

testnet_system_contract_id = "CF9Nd9wvQ8qVsGk8jYHbj6sf8TK7MJ2GYgt"

payment_channel_contract_id = "<your_payment_channel_contract_id>"

deposit_function_id = system_contract_helper.deposit_function_index

sys_deposit_data_stack = system_contract_helper.deposit_data_stack_generator(sender.address, payment_channel_contract_id, <your_deposit_amount>)

sender.execute_contract(testnet_system_contract_id, deposit_function_id, sys_deposit_data_stack)

After depositing VSYS into the contract, I execute the System Contract once more to withdraw VSYS from the payment channel contract.

# sysWithdraw

testnet_system_contract_id = "CF9Nd9wvQ8qVsGk8jYHbj6sf8TK7MJ2GYgt"

payment_channel_contract_id = "<your_payment_channel_contract_id>"

withdraw_function_id = system_contract_helper.withdraw_function_index

sys_withdraw_data_stack = system_contract_helper.withdraw_data_stack_generator(payment_channel_contract_id, sender.address, <your_withdraw_amount>)

sender.execute_contract(testnet_system_contract_id, withdraw_function_id, sys_withdraw_data_stack)