Factory contracts

Factory contracts are smart contracts that can deploy other smart contracts. This pattern enables powerful use cases like creating token contracts on demand, deploying user-specific contracts, or building contract templates.

Overview

A factory contract:

Stores the WASM code of contracts it can deploy
Creates new contract accounts
Deploys code to those accounts
Optionally initializes the deployed contracts

GitHub Repository

View the complete factory contract example

How it works

Store contract WASM

The factory stores the binary code of contracts it will deploy:

Rust
JavaScript

use near_sdk::{near, env, Promise, AccountId};
use near_sdk::store::Vector;

#[near(contract_state)]
pub struct Factory {
    code: Vec<u8>,
}

#[near]
impl Factory {
    #[init]
    pub fn new(code: Vec<u8>) -> Self {
        Self { code }
    }
    
    pub fn update_code(&mut self, code: Vec<u8>) {
        self.code = code;
    }
}

import { NearBindgen, near, initialize, call } from 'near-sdk-js';

@NearBindgen({})
class Factory {
  code: Uint8Array;
  
  @initialize({})
  init({ code }) {
    this.code = code;
  }
  
  @call({})
  update_code({ code }) {
    this.code = code;
  }
}

Create new accounts

The factory creates sub-accounts and deploys contracts to them:

Rust
JavaScript

#[near]
impl Factory {
    #[payable]
    pub fn create_contract(
        &self,
        name: String,
        args: Vec<u8>,
    ) -> Promise {
        let account_id: AccountId = format!(
            "{}.{}",
            name,
            env::current_account_id()
        )
        .parse()
        .unwrap();
        
        let attached_deposit = env::attached_deposit();
        
        Promise::new(account_id.clone())
            .create_account()
            .transfer(attached_deposit)
            .deploy_contract(self.code.clone())
            .function_call(
                "init".to_string(),
                args,
                0,
                Gas::from_tgas(30),
            )
    }
}

@call({ payableFunction: true })
create_contract({ name, args }) {
  const accountId = `${name}.${near.currentAccountId()}`;
  const deposit = near.attachedDeposit();
  
  const promise = near.promiseBatchCreate(accountId);
  near.promiseBatchActionCreateAccount(promise);
  near.promiseBatchActionTransfer(promise, deposit);
  near.promiseBatchActionDeployContract(promise, this.code);
  near.promiseBatchActionFunctionCall(
    promise,
    "init",
    args,
    0,
    30000000000000
  );
  
  return promise;
}

Deploy and test

# Deploy the factory
near contract deploy factory.testnet use-file ./factory.wasm

# Store the contract code to deploy
near contract call-function as-transaction factory.testnet \
  update_code \
  file-args contract.wasm \
  prepaid-gas '300 TeraGas' \
  attached-deposit '0 NEAR' \
  network-config testnet

# Create a new contract instance
near contract call-function as-transaction factory.testnet \
  create_contract \
  json-args '{"name":"my-contract","args":{}}' \
  prepaid-gas '300 TeraGas' \
  attached-deposit '3 NEAR' \
  network-config testnet

Use cases

Token factories

Deploy new FT or NFT contracts on demand for users or projects

DAO factories

Create DAO contracts with custom governance rules

Game instances

Spawn isolated game session contracts

User contracts

Deploy personal contracts for each user (e.g., wallets, vaults)

Best practices

Account naming

Choose a clear naming convention for deployed contracts:

Use meaningful prefixes: token.factory.near
Include version numbers if needed: v1.token.factory.near
Consider uniqueness: append timestamps or counters
Sub-accounts cost storage, factor into deposit requirements

Storage costs

Creating accounts and deploying contracts requires NEAR deposits:

Account creation: ~0.00182 NEAR minimum
Code storage: ~0.0001 NEAR per byte
State storage: depends on contract initialization
Always require sufficient deposit in create_contract

Code updates

Plan for updating the contract template:

Implement update_code with proper access control
Consider versioning: maintain multiple templates
Test thoroughly before updating production code
Document breaking changes

Security considerations

Protect your factory from abuse:

Limit who can create contracts (whitelist, fees, etc.)
Validate contract initialization parameters
Consider rate limiting
Monitor for suspicious patterns

Advanced patterns

Versioned deployments

Maintain multiple contract versions:

#[near(contract_state)]
pub struct Factory {
    versions: UnorderedMap<String, Vec<u8>>,
}

#[near]
impl Factory {
    pub fn add_version(&mut self, version: String, code: Vec<u8>) {
        self.versions.insert(version, code);
    }
    
    #[payable]
    pub fn create_contract_version(
        &self,
        version: String,
        name: String,
        args: Vec<u8>,
    ) -> Promise {
        let code = self.versions.get(&version).expect("Version not found");
        // ... deploy with specific version
    }
}

Access control

Restrict who can create contracts:

#[near(contract_state)]
pub struct Factory {
    owner: AccountId,
    whitelist: UnorderedSet<AccountId>,
}

#[near]
impl Factory {
    #[payable]
    pub fn create_contract(&self, name: String) -> Promise {
        let caller = env::predecessor_account_id();
        require!(
            self.whitelist.contains(&caller),
            "Not authorized to create contracts"
        );
        // ... create contract
    }
}

Callback tracking

Track deployed contracts:

#[near(contract_state)]
pub struct Factory {
    deployed_contracts: Vector<AccountId>,
}

#[near]
impl Factory {
    #[private]
    pub fn on_contract_created(&mut self, account_id: AccountId) {
        if env::promise_results_count() == 1 {
            match env::promise_result(0) {
                PromiseResult::Successful(_) => {
                    self.deployed_contracts.push(account_id);
                    log!("Contract deployed successfully");
                }
                _ => log!("Contract deployment failed"),
            }
        }
    }
    
    pub fn get_deployed_contracts(&self) -> Vec<AccountId> {
        self.deployed_contracts.iter().collect()
    }
}

Testing factory contracts

Rust
JavaScript

#[tokio::test]
async fn test_factory_deployment() -> Result<()> {
    let worker = near_workspaces::sandbox().await?;
    let factory_wasm = std::fs::read("factory.wasm")?;
    let contract_wasm = std::fs::read("contract.wasm")?;
    
    // Deploy factory
    let factory = worker.dev_deploy(&factory_wasm).await?;
    
    // Initialize with contract code
    factory
        .call("new")
        .args_borsh(contract_wasm.clone())
        .transact()
        .await?;
    
    // Create a new contract
    let outcome = factory
        .call("create_contract")
        .args_json(serde_json::json!({
            "name": "test-contract",
            "args": "{}"
        }))
        .deposit(near_sdk::NearToken::from_near(5))
        .transact()
        .await?;
    
    assert!(outcome.is_success());
    
    Ok(())
}

import { Worker } from 'near-workspaces';

test('factory deploys contracts', async () => {
  const worker = await Worker.init();
  const root = worker.rootAccount;
  
  // Deploy factory
  const factory = await root.devDeploy('factory.wasm');
  const contractCode = await fs.readFile('contract.wasm');
  
  // Initialize factory
  await factory.call('init', { code: contractCode });
  
  // Create new contract
  await factory.call(
    'create_contract',
    { name: 'test', args: {} },
    { attachedDeposit: '5000000000000000000000000' }
  );
  
  // Verify deployment
  const deployed = await factory.view('get_deployed_contracts', {});
  expect(deployed).toContain('test.' + factory.accountId);
});

Next steps

Update contracts

Learn how to update deployed contracts

Cross-contract calls

Interact with deployed contracts

DAO primitives

Use factories to create DAOs

Contract standards

Implement standard interfaces

Protocol Basics

Smart Contracts

Multi-Chain

Full Stack

Overview

GitHub Repository

How it works

Use cases

Token factories

DAO factories

Game instances

User contracts

Best practices

Advanced patterns

Versioned deployments

Access control

Callback tracking

Testing factory contracts

Next steps

Update contracts

Cross-contract calls

DAO primitives

Contract standards

Build docs developers (and LLMs) love

Protocol Basics

Smart Contracts

Multi-Chain

Full Stack

​Overview

GitHub Repository

​How it works

​Use cases

Token factories

DAO factories

Game instances

User contracts

​Best practices

​Advanced patterns

​Versioned deployments

​Access control

​Callback tracking

​Testing factory contracts

​Next steps

Update contracts

Cross-contract calls

DAO primitives

Contract standards

Build docs developers (and LLMs) love

Overview

How it works

Use cases

Best practices

Advanced patterns

Versioned deployments

Access control

Callback tracking

Testing factory contracts

Next steps