How to compile a contract
Once you have written a contract in Aztec.nr, you will need to compile it into an artifact in order to use it.
In this guide we will cover how to do so, both using the aztec-nargo command and programmatically.
We'll also cover how to generate a helper TypeScript interface and an Aztec.nr interface for easily interacting with your contract from your typescript app and from other Aztec.nr contracts, respectively.
Compile using aztec-nargo
To compile a contract using the Aztec's build of nargo.
Run the aztec-nargo compile command within your contract project folder, which is the one that contains the Nargo.toml file:
aztec-nargo compile
This will output a JSON artifact for each contract in the project to a target folder containing the Noir ABI artifacts.
This command looks for Nargo.toml files by ascending up the parent directories, and will compile the top-most Nargo.toml file it finds.
Eg: if you are in /hobbies/cool-game/contracts/easter-egg/, and both cool-game and easter-egg contain a Nargo.toml file, then aztec-nargo compile will be performed on cool-game/Nargo.toml and compile the project(s) specified within it. Eg
[workspace]
members = [
"contracts/easter-egg",
]
Typescript Interfaces
You can use the code generator to autogenerate type-safe typescript classes for each of your contracts. These classes define type-safe methods for deploying and interacting with your contract based on their artifact.
aztec-builder codegen ./aztec-nargo/output/target/path -o src/artifacts
Below is typescript code generated from the Token contract:
export class TokenContract extends ContractBase {
private constructor(instance: ContractInstanceWithAddress, wallet: Wallet) {
super(instance, TokenContractArtifact, wallet);
}
/**
* Creates a contract instance.
* @param address - The deployed contract's address.
* @param wallet - The wallet to use when interacting with the contract.
* @returns A promise that resolves to a new Contract instance.
*/
public static async at(address: AztecAddress, wallet: Wallet) {
return Contract.at(address, TokenContract.artifact, wallet) as Promise<TokenContract>;
}
/**
* Creates a tx to deploy a new instance of this contract.
*/
public static deploy(
wallet: Wallet,
admin: AztecAddressLike,
name: string,
symbol: string,
decimals: bigint | number,
) {
return new DeployMethod<TokenContract>(
Fr.ZERO,
wallet,
TokenContractArtifact,
TokenContract.at,
Array.from(arguments).slice(1),
);
}
/**
* Creates a tx to deploy a new instance of this contract using the specified public keys hash to derive the address.
*/
public static deployWithPublicKeysHash(
publicKeysHash: Fr,
wallet: Wallet,
admin: AztecAddressLike,
name: string,
symbol: string,
decimals: bigint | number,
) {
return new DeployMethod<TokenContract>(
publicKeysHash,
wallet,
TokenContractArtifact,
TokenContract.at,
Array.from(arguments).slice(2),
);
}
/**
* Creates a tx to deploy a new instance of this contract using the specified constructor method.
*/
public static deployWithOpts<M extends keyof TokenContract['methods']>(
opts: { publicKeysHash?: Fr; method?: M; wallet: Wallet },
...args: Parameters<TokenContract['methods'][M]>
) {
return new DeployMethod<TokenContract>(
opts.publicKeysHash ?? Fr.ZERO,
opts.wallet,
TokenContractArtifact,
TokenContract.at,
Array.from(arguments).slice(1),
opts.method ?? 'constructor',
);
}
/**
* Returns this contract's artifact.
*/
public static get artifact(): ContractArtifact {
return TokenContractArtifact;
}
public static get storage(): ContractStorageLayout<
| 'admin'
| 'minters'
| 'balances'
| 'total_supply'
| 'pending_shields'
| 'public_balances'
| 'symbol'
| 'name'
| 'decimals'
> {
return {
admin: {
slot: new Fr(1n),
typ: 'PublicMutable<AztecAddress>',
},
minters: {
slot: new Fr(2n),
typ: 'Map<AztecAddress, PublicMutable<bool>>',
},
balances: {
slot: new Fr(3n),
typ: 'BalancesMap<TokenNote>',
},
total_supply: {
slot: new Fr(4n),
typ: 'PublicMutable<U128>',
},
pending_shields: {
slot: new Fr(5n),
typ: 'PrivateSet<TransparentNote>',
},
public_balances: {
slot: new Fr(6n),
typ: 'Map<AztecAddress, PublicMutable<U128>>',
},
symbol: {
slot: new Fr(7n),
typ: 'SharedImmutable<FieldCompressedString>',
},
name: {
slot: new Fr(8n),
typ: 'SharedImmutable<FieldCompressedString>',
},
decimals: {
slot: new Fr(9n),
typ: 'SharedImmutable<u8>',
},
} as ContractStorageLayout<
| 'admin'
| 'minters'
| 'balances'
| 'total_supply'
| 'pending_shields'
| 'public_balances'
| 'symbol'
| 'name'
| 'decimals'
>;
}
public static get notes(): ContractNotes<'TransparentNote' | 'TokenNote'> {
const notes = this.artifact.outputs.globals.notes ? (this.artifact.outputs.globals.notes as any) : [];
return {
TransparentNote: {
id: new Fr(84114971101151129711410111011678111116101n),
},
TokenNote: {
id: new Fr(8411110710111078111116101n),
},
} as ContractNotes<'TransparentNote' | 'TokenNote'>;
}
/** Type-safe wrappers for the public methods exposed by the contract. */
public override methods!: {
/** transfer_public(from: struct, to: struct, amount: field, nonce: field) */
transfer_public: ((
from: AztecAddressLike,
to: AztecAddressLike,
amount: FieldLike,
nonce: FieldLike,
) => ContractFunctionInteraction) &
Pick<ContractMethod, 'selector'>;
/** transfer(from: struct, to: struct, amount: field, nonce: field) */
transfer: ((
from: AztecAddressLike,
to: AztecAddressLike,
amount: FieldLike,
nonce: FieldLike,
) => ContractFunctionInteraction) &
Pick<ContractMethod, 'selector'>;
...
};
}
Read more about interacting with contracts using aztec.js here.
Aztec.nr interfaces
An Aztec.nr contract can call a function in another contract via context.call_private_function or context.call_public_function. However, this requires manually assembling the function selector and manually serializing the arguments, which is not type-safe.
To make this easier, the compiler automatically generates interface structs that expose a convenience method for each function listed in a given contract artifact. These structs are intended to be used from another contract project that calls into the current one.
Below is an example of interface usage generated from the Token contract, used from the FPC:
contract FPC {
...
use dep::token::Token;
...
#[aztec(private)]
fn fee_entrypoint_private(amount: Field, asset: AztecAddress, secret_hash: Field, nonce: Field) {
assert(asset == storage.other_asset.read_private());
Token::at(asset).unshield(context.msg_sender(), context.this_address(), amount, nonce).call(&mut context);
FPC::at(context.this_address()).pay_fee_with_shielded_rebate(amount, asset, secret_hash).enqueue(&mut context);
}
#[aztec(private)]
fn fee_entrypoint_public(amount: Field, asset: AztecAddress, nonce: Field) {
FPC::at(context.this_address()).prepare_fee(context.msg_sender(), amount, asset, nonce).enqueue(&mut context);
FPC::at(context.this_address()).pay_fee(context.msg_sender(), amount, asset).enqueue(&mut context);
}
...
}
Read more about how to use the Aztec.nr interfaces here.
At the moment, the compiler generates these interfaces from already compiled ABIs, and not from source code. This means that you should not import a generated interface from within the same project as its source contract, or you risk circular references.
Next steps
Once you have compiled your contracts, you can use the generated artifacts via the Contract class in the aztec.js package to deploy and interact with them, or rely on the type-safe typescript classes directly.