State
type State<A>: {
"fetch": Promise<undefined | A>;
"fromAppState": A;
"get": A;
"getAndRequireEquals": A;
"requireEquals": void;
"requireEqualsIf": void;
"requireNothing": void;
"set": void;
};
Gettable and settable state that can be checked for equality.
Type parameters
• A
Type declaration
fetch()
Asynchronously fetch the on-chain state. This is intended for getting the state outside a smart contract.
Returns
Promise\<undefined | A>
fromAppState()
Get the state from the raw list of field elements on a zkApp account, for example:
let myContract = new MyContract(address);
let account = Mina.getAccount(address);
let x = myContract.x.fromAppState(account.zkapp!.appState);
Parameters
• appState: Field[]
Returns
A
get()
Get the current on-chain state.
Caution: If you use this method alone inside a smart contract, it does not prove that your contract uses the current on-chain state.
To successfully prove that your contract uses the current on-chain state, you must add an additional .requireEquals() statement or use .getAndRequireEquals():
let x = this.x.get();
this.x.requireEquals(x);
OR
let x = this.x.getAndRequireEquals();
Returns
A
getAndRequireEquals()
Get the current on-chain state and prove it really has to equal the on-chain state, by adding a precondition which the verifying Mina node will check before accepting this transaction.
Returns
A
requireEquals()
Prove that the on-chain state has to equal the given state, by adding a precondition which the verifying Mina node will check before accepting this transaction.
Parameters
• a: A
Returns
void
requireEqualsIf()
Require that the on-chain state has to equal the given state if the provided condition is true.
If the condition is false, this is a no-op. If the condition is true, this adds a precondition that the verifying Mina node will check before accepting this transaction.
Parameters
• condition: Bool
• a: A
Returns
void
requireNothing()
DANGER ZONE: Override the error message that warns you when you use .get() without adding a precondition.
Returns
void
set()
Set the on-chain state to a new value.
Parameters
• a: A
Returns
void