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CosmWasm - GitPod

link

Terra Academy

https://academy.terra.money/courses/take/cosmwasm-smart-contracts-i/lessons/26696356-intro-to-cosmwasm

Messages in CosmWasm

Before you view the Quick Start Contract Walkthrough, it's helpful to talk briefly about messages. Cosmos blockchains operate by sending various kinds messages around. Messages are sent from users to contracts, from contracts to contracts, and even from contracts to other blockchain. Blockchain platforms are, after all, protocols for sending, processing, and logging authorized messages around. Most of these messages are commands to do something, but some are just queries for information.

We'll see a lot of CosmosMsg messages in our contract work, including:

  • BankMsg
  • StakingMsg
  • DistributionMsg
  • IbcMsg
  • WasmMsg
  • GovMsg

But the primary types of messages we need to worry about are the messages interacting with our smart contract.

All smart contracts need to handle three kinds of incoming messages:

  • InstantiateMsg: what happens when an instance of a smart contract is created (startup code)
  • ExecuteMsg: the kinds of actions users can tell a smart contract to execute (write operations)
  • QueryMsg: the kinds of queries for information users can send to a smart contract (read operations)

Incoming messages of these three types will be passed off to our contract's entry points: the instantiate(), execute(), and query() functions. These may be indicated in the template you pull with the macro attribute

#[entry_point]

which you should now replace with:

#[cfg_attr(not(feature = "library"), entry_point)]

All of our core code will be located in these three functions, or in functions called by these three functions.

Quick Start: CosmWasm Contract Walkthrough

NOTE: In order for this tutorial to generate the template smart contract correctly, make sure you run this command from terminal:

cargo install cargo-generate --features vendored-openssl

ALSO: Note that instead of the #[entry_point] macro attribute, the following should now be used as of CosmWasm 0.16:

#[cfg_attr(not(feature = "library"), entry_point)]

We can learn a lot about CosmWasm smart contracts – and get a good start on our own – by pulling the CosmWasm Template Smart Contract.

For experienced programmers, this is the perfect video to get started.

For beginners, you should watch this video, but it and the accompanying exercise may be a little too much for you. If so, no worries! Come back once you've completed more of the main course content and exercises, and you should find yourself easily following along with the concepts.

cargo test
cargo schema
cargo fmt --all -- --check

Installing Rust

curl https://sh.rustup.rs | bash

Learn Rust with Rustlings

sudo apt update
sudo apt install build-essential
curl -L https://git.io/install-rustlings | bash
cd rustlings
code .
rustlings watch