The `require_recipient` function

The function is declared in action.codon as follows:

def require_recipient(account: Name):

The require_recipient function is utilized to notify other contracts. If the account contract has the same action, this action will be called.

The following code in sender.codon and receiver.codon demonstrates how to send a notification from one contract to another.

# sender.codon
from chain.name import Name
from chain.contract import Contract
from chain.action import require_recipient

@contract(main=True)
class MyContract(Contract):

    @action('sayhello')
    def sayhello(self, receiver: Name):
        print('hello, world')
        require_recipient(receiver)

# receiver.codon
from chain.name import Name
from chain.contract import Contract

@contract(main=True)
class MyContract(Contract):

    @action('sayhello', notify=True)
    def sayhello(self, receiver: Name):
        assert not self.receiver == self.first_receiver
        assert receiver == self.receiver
        print('hello, world from notify')

Note that the definition of the sayhello function in receiver.codon is slightly different from that in sender.codon. The notify=True in the action decorator of the sayhello function in receiver.codon is used to specify that this action is used to receive notifications and can only be triggered by calling require_recipient.

The following is the test code:

def init_notify():
    t = ChainTester(True)
    update_auth(t, 'hello')

    wasm_file = os.path.join(dir_name, 'notify/sender.wasm')
    with open(wasm_file, 'rb') as f:
        code = f.read()
    abi_file = os.path.join(dir_name, 'notify/sender.abi')
    with open(abi_file, 'r') as f:
        abi = f.read()
    t.deploy_contract('hello', code, abi)
    t.produce_block()

    wasm_file = os.path.join(dir_name, 'notify/receiver.wasm')
    with open(wasm_file, 'rb') as f:
        code = f.read()
    abi_file = os.path.join(dir_name, 'notify/receiver.abi')
    with open(abi_file, 'r') as f:
        abi = f.read()
    t.deploy_contract('alice', code, abi)
    t.produce_block()
    return t

def test_notify():
    t = init_notify()
    args = {'receiver': 'alice'}
    ret = t.push_action('hello', 'sayhello', args, {'hello': 'active'})
    t.produce_block()
    logger.info("++++++++++%s\n", ret['elapsed'])

Compile:

python-contract build notify/receiver.codon
python-contract build notify/sender.codon

Test:

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

Output:

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

[(hello,sayhello)->hello]: CONSOLE OUTPUT END   =====================
debug 2023-03-28T13:08:01.110 thread-0  apply_context.cpp:30          print_debug          ] 
[(hello,sayhello)->alice]: CONSOLE OUTPUT BEGIN =====================
hello, world from notify

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

The require_recipient function

The `require_recipient` function