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Version: 3.x.x

ink! vs. CosmWasm

This is a short comparison between ink! and CosmWasm meant to onboard developers coming from the Cosmos ecosystem.

Architecture

CosmWasm is modular, meaning that any blockchain using the Cosmos SDK can add smart contract support to their chain. That is similar to the Substrate approach, where chains have the option to add pallet-contracts to their runtime.

Aside from that, the architecture philosophy is likely the point where CosmWasm and ink! differ the most. CosmWasm follows the actor model design pattern, while ink! follows a synchronous execution model. That means some fundamental differences in how the source code is structured.

The main entry point functions of CosmWasm contracts are:

  • instantiate which bootstraps the initial contract state (assuming it's already been deployed).
  • execute which has the actor perform operations to its internal state.
  • query which retrieves data from the actor’s internal state.

An ink! contract can have as many public dispatchables as the developer desires, and differently from CosmWasm, it doesn’t rely on JSON schemas for defining how the messages are structured.

Instead, ink! makes heavy usage of Rust macros. The main ink! macros are:

  • #[ink(constructor)] which is called when the contract is deployed, and is responsible for bootstrapping the initial contract state into the storage. It is analogous to the CosmWasm instantiate function.
  • #[ink(storage)] which annotates a struct that represents the contract's internal state.
  • #[ink(message)] which marks a function as a public dispatchable, meaning that it is exposed in the contract interface to the outside world. This macro can make a function behave analogously to CosmWasm’s execute and query functions. This depends on how it affects the internal contract state and what the return types.
  • #[ink(event)] and #[ink(topic)] which annotates a struct and its members as the events and topics that the contract might emit.

There are other ink! macros, for which details can be found at Macros & Attributes.

Unit Testing

Unit testing in CosmWasm is quite similar to ink!. Both use the conventional Rust #[cfg(test)] macro and set up a mock on-chain environment.

While CosmWasm unit tests have different modules for each of the three main entry-point functions, ink! allows for a more generalised approach, where the #[ink(test)] macro is used for each unit test.

You can read more about ink! unit tests here.

Compiler

CosmWasm uses cargo-wasm as its main compiler, while ink! uses cargo-contract. cargo-contract is developed by Parity specifically for building, testing, and deploying ink! contracts.

Local Development Network

In terms of local development networks, the cosmos/gaia repository acts as the basic template for a generic Cosmos node. With the addition of the x/wasm module and some clean-up, this template repository becomes wasmd, the entry point for CosmWasm development.

In terms of Substrate, substrate-node-template is a basic generic template of a node. Similar to x/wasm, [pallet-contracts[(https://github.com/paritytech/substrate/tree/master/frame/contracts) is the module that adds WebAssembly smart contract functionality to the chain. Parity provides the substrate-contracts-node, which is analogous to wasmd - a basic template node for smart contract development.

Testnets

For CosmWasm development and on-chain testing, wasmd can be operated as a local setup (single or multiple nodes), or connected to the cliffnet public test network.

ink! contracts can be deployed on a few different options:

Development Workflow

Dependencies

The first step in CosmWasm development is to install dependencies, namely Go, Rust and wasmd.

For ink! you can also find a setup guide which will help you with dependencies, namely Rust, cargo-contract and substrate-contracts-node.

Environment Setup

The next step in the CosmWasm development workflow is setting up the environment. That consists mainly of configuring wasmd such that it has prefunded accounts that are able to interact with the network.

When substrate-contracts-node is started with the --dev flag, it already contains well known pre-funded accounts (alice, bob, etc.) which are ready to be used for development.

Compile and Test

CosmWasm provides example contracts at the cw-contracts repository. After the repository is cloned, from the contract directory it can be compiled via:

$ cargo wasm

and tested via:

$ cargo unit-test

Similarly, ink! provides an examples directory of its main repository.

A contract can be compiled from its directory via:

$ cargo +nightly contract build

and tested via:

$ cargo test

Deploy and Interact

CosmWasm contracts are deployed and instantiated with help of the wasmd executable. The list of step is provided here.

It is possible to deploy and interact with ink! contracts using either a CLI (cargo-contract), or a web UI (contracts-ui).