Common Smart Contract Functions
isAccount
Declaration:
function isAccount(name: Name): bool
Description:
Used to determine whether an account exists or not.
hasAuth
Declaration:
function hasAuth(name: Name): bool
Description:
Used to determine whether it has the active permission of a specified account, that is, whether the Transaction has been signed with the private key corresponding to the active permission of the specified account. The private key used for signing may be at least one, or two or more.
requireAuth/requireAuth2
Declaration:
function requireAuth(name: Name): void
function hasAuth(name: Name): bool
function requireAuth2(permissionLevel: PermissionLevel): void
Description:
These two functions will throw exceptions if the account does not exist or if the specified account's permission is not detected. The difference is that requireAuth checks for the existence of active permission, while requireAuth2 can check for specified permissions. Among them, the requireAuth function is used very frequently in contract development to ensure that the execution of an action has the active permission of a certain account.
currentTime
Declaration:
function currentTime(): u64
Description:
Used to get the time of the block where the Transaction is located, in microseconds (1 second equals 1,000,000 microseconds).
check
Declaration:
function check(test: bool, msg: string): void
Description:
If test is false, it will throw an exception, all actions executed in the Transaction and the operations on the database that have been executed by this action will be rolled back, and the Transaction will not be chained. This is quite different from the revert mechanism in Ethereum. The result is that the EOS network is relatively vulnerable, because the rollback of the exceptional Transaction does not consume resources, that is, it does not incur costs, making the network more susceptible to attacks. But in normal contracts, this function is also frequently used in smart contracts, you can refer to the related code in eosio.token.contract.ts
Example Code:
import {
Name,
PermissionLevel,
Contract,
requireAuth,
requireAuth2,
hasAuth,
isAccount,
print,
check
} from "asm-chain";
@contract
class MyContract extends Contract {
constructor(receiver: Name, firstReceiver: Name, action: Name) {
super(receiver, firstReceiver, action);
}
@action("test")
test(): void {
let ret = isAccount(Name.fromString("noexits"));
print(`+++isAccount(noexits): ${ret}\n`);
ret = isAccount(this.receiver);
print(`+++isAccount(this.receiver): ${ret}\n`);
print(`hasAuth: ${hasAuth(this.receiver)}`);
requireAuth(this.receiver);
requireAuth2(new PermissionLevel(this.receiver, Name.fromString("active")));
}
}
Compilation:
cd examples/commonfunctions
yarn
yarn build
Test code:
@chain_test
def test_hello(tester):
deploy_contract(tester, 'test')
args = {}
r = tester.push_action('hello', 'test', args, {'hello': 'active'})
logger.info('++++++elapsed: %s', r['elapsed'])
tester.produce_block()
Testing:
ipyeos -m pytest -s -x test.py -k test_hello
Output:
[(hello,test)->hello]: CONSOLE OUTPUT BEGIN =====================
+++isAccount(noexits): false
+++isAccount(this.receiver): true
hasAuth: true
current time: 1527854403000000
[(hello,test)->hello]: CONSOLE OUTPUT END =====================