LogoLogo
  • WELCOME TO ALEPH ZERO
  • EXPLORE
    • About Aleph Zero
    • AlephBFT Consensus
    • The Economy of Aleph Zero
    • Where to Buy AZERO
    • Decentralized Governance on Aleph Zero
    • Ecosystem
    • Aleph Zero Foundation Treasury Management
    • Community
    • Glossary
    • Audit & Research Papers
  • USE
    • Wallets
    • Explorer
    • Ledger
    • Telegram Notifications
    • Aleph Zero Signer
      • General introduction
      • What does Signer do?
      • What are Sub-accounts and Sub-account paths?
      • Why is it critical to store your Secret Phrase in a safe place?
      • How to forget and restore accounts?
      • What are Networks?
      • What are Trusted apps?
    • Dashboard
      • Dashboard basics
      • Overview
    • Stake
      • Staking Basics
      • Staking Menu Overview
      • How to Start Staking with the Aleph Zero Dashboard
      • How to Start Staking With the Developer Wallet
      • How to start staking using Ledger hardware wallet
      • How to Change Nominations
      • How to Stop Staking
      • Staking Rewards
      • Validators
      • Commission and Foundation Nodes
      • Proxy Accounts
    • Validate
      • Validating Overview
      • Hardware requirements
      • Running an Aleph Node on Testnet
        • Downloading and running the node
        • Verifying your setup
        • Customizing your setup
        • Building and running from source [advanced]
          • Building from source
          • Set environment variables
          • Download DB snapshot
          • Running the binary
        • Appendix: Ports, addresses, validators, and archivists
      • Running an Aleph Node on Mainnet
        • Running the node
        • Building and running from source [advanced]
      • Setting your identity
      • Making the node validate
      • Securing your validator
      • Troubleshooting
      • Elections and Rewards Math
      • Testnet Validator Airdrop
      • Foundation Nomination Program
    • Using the EVM-layer
    • Governance
      • Token
      • Multisig Accounts
  • BUILD
    • Aleph Zero smart contracts basics
      • Setting up a Testnet account
      • Installing required tools
      • Creating your first contract
      • Deploying your contract to Aleph Zero Testnet
      • Extending your contract
    • Cross contract calls
      • Using references
      • Using dynamic calls
    • Migrating from Solidity
    • Writing e2e tests with ink-wrapper
    • Aleph Zero Signer integration
    • Front-end app: smart contract interaction
    • Security Course by Kudelski Security
      • ink! Developers Security Guideline
      • Lesson 1 - Getting started with ink!
      • Lesson 2 - Threat Assessment
      • Lesson 3 - Integer Overflow
      • Lesson 4 - Signed-integer
      • Lesson 5 - Role-Based Access Control
      • Lesson 6 - Address Validation
      • Lesson 7 - Smart Contract Control
    • Development on EVM-layer
  • PROTOCOL DETAILS
    • Shielder
      • Overview
      • Design against Bad Actors
      • Preliminaries - ZK-relations
      • Notes and Accounts
      • ZK-ID and Registrars
      • Anonymity Revokers
      • PoW Anonymity Revoking
      • Relayers
      • Deterministic Secret Management
      • SNARK-friendly Symmetric Encryption
      • SNARK-friendly Asymmetric Encryption
      • Cryptography
      • Token shortlist
      • User Wallet
      • Versioning
      • PoC
      • Version 0.1.0
      • Version 0.2.0
    • Common DEX
      • Common Whitepaper - Differences
      • Dutch Auctions
  • FAQ
  • Tutorials
    • Withdrawing coins from exchanges
      • How to withdraw your AZERO coins from KuCoin
      • How to withdraw your AZERO coins from MEXC Global
      • How to withdraw your AZERO coins from HTX
  • Setting up or restoring a wallet
    • How to set up or recover your AZERO account using Aleph Zero Signer
    • How to set up or recover your AZERO account using the official mainnet web wallet
    • How to set up or recover your AZERO account using Nova Wallet
    • How to set up or recover your AZERO account using SubWallet
    • How to set up or recover your AZERO account using Talisman
  • Staking
    • How to stake via a direct nomination using the Aleph Zero Dashboard
    • How to stake via a nomination pool using the Aleph Zero Dashboard
    • How to destroy a nomination pool via the Aleph Zero Dashboard
Powered by GitBook
On this page
  • Basics
  • The examples

Was this helpful?

  1. BUILD

Cross contract calls

This section covers the more advanced topic of calling another contract from your code.

PreviousExtending your contractNextUsing references

Last updated 2 years ago

Was this helpful?

Before we start, you may want to check out our : all the code you will find in this tutorial is there in its full form. The examples in there are not limited to cross-contract calls and cover almost every aspect of smart contract development, so we encourage you to study it in addition to reading this guide.

The ability of smart contracts to call methods of another contract is arguably one of the most powerful concepts offered by Ink!. For example, a DEX will need to call the transfer_from method of a PSP22 token. However, this is also a feature that requires a lot of care during implementation.

Basics

Ink! offers two ways of calling another contract, each with a different set of trade-offs:

  • importing a reference to another contract and using it almost like any other method:

    • very convenient

    • the compiler is able to check whether a method you want to call exists and if the parameter types match

    • it doesn't allow you to dynamically construct calls

    • it doesn't allow you to send tokens with the call

  • dynamically building a call (the CallBuilder method):

    • a lot of control over the execution

    • it allows for sending tokens along with the call

    • it allows for dynamically choosing a method to call

    • the compiler is not able to assist you in creating a valid call so you need to be extra careful

While the choice of a particular method may be a matter of personal preference, we suggest using the references by default and choosing the CallBuilder only if you really need it.

The examples

In the two subsequent sections, we will use the BulletinBoard contract as an example. The contract allows users to post pieces of text ('bulletins') to the board and highlight selected posts. The highlighted posts are tracked by a separate contract: HighlightedPosts.

The split between the two contracts is pretty arbitrary and not really necessary for this logic to work. However, it serves a higher purpose of demonstrating cross-contract calls in an easy-to-understand example.

Bulletin Board Example repository