HelloWorld

The First Smart Contract

Below is a simple example of a smart contract code and its corresponding test code.

Full Example

import {
    Name,
    Contract,
    print,
} from "asm-chain";

@contract
class MyContract extends Contract {
    constructor(receiver: Name, firstReceiver: Name, action: Name) {
        super(receiver, firstReceiver, action);
    }

    @action("sayhello")
    say_hello(): void {
        print("++++++++hello, world\n");
    }
}

Test code:

import os
import sys
import json
import struct
import pytest

test_dir = os.path.dirname(__file__)
sys.path.append(os.path.join(test_dir, '..'))

from ipyeos import log
from ipyeos import chaintester
from ipyeos.chaintester import ChainTester

chaintester.chain_config['contracts_console'] = True

logger = log.get_logger(__name__)

def update_auth(tester, account):
    a = {
        "account": account,
        "permission": "active",
        "parent": "owner",
        "auth": {
            "threshold": 1,
            "keys": [
                {
                    "key": 'EOS6AjF6hvF7GSuSd4sCgfPKq5uWaXvGM2aQtEUCwmEHygQaqxBSV',
                    "weight": 1
                }
            ],
            "accounts": [{"permission":{"actor":account,"permission": 'eosio.code'}, "weight":1}],
            "waits": []
        }
    }
    tester.push_action('eosio', 'updateauth', a, {account:'active'})

def init_tester():
    tester = chaintester.ChainTester()
    update_auth(tester, 'hello')
    return tester

def chain_test(fn):
    def call():
        tester = init_tester()
        ret = fn(tester)
        tester.free()
        return ret
    return call

class NewChainTester():
    def __init__(self):
        self.tester = None

    def __enter__(self):
        self.tester = init_tester()
        return self.tester

    def __exit__(self, type, value, traceback):
        self.tester.free()

test_dir = os.path.dirname(__file__)
def deploy_contract(tester, package_name):
    with open(f'{test_dir}/assembly/target/{package_name}.wasm', 'rb') as f:
        code = f.read()
    with open(f'{test_dir}/assembly/target/{package_name}.abi', 'rb') as f:
        abi = f.read()
    tester.deploy_contract('hello', code, abi)

@chain_test
def test_hello(tester):
    deploy_contract(tester, 'helloworld')
    args = {}
    r = tester.push_action('hello', 'sayhello', args, {'hello': 'active'})
    logger.info('++++++elapsed: %s', r['elapsed'])
    tester.produce_block()

Compile:

cd examples/helloworld
yarn
yarn build

Run test code:

ipyeos -m pytest -s -x test.py -k test_hello

Or run:

yarn pytest

Output:

[(hello,sayhello)->hello]: CONSOLE OUTPUT BEGIN =====================
hello,world!

[(hello,sayhello)->hello]: CONSOLE OUTPUT END   =====================

Note that the above output is debugging information. If running on the mainnet, the output of the print function is not visible. If running on the testnet, you need to add the --contracts-console parameter when running the nodeos command to see the debug output.

In the above test code, the debug information is outputted directly by this line of code:

chaintester.chain_config['contracts_console'] = True

Additionally, in the released version of the code, to improve the performance of program execution, you should not include print related code.

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