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Create Counter project

This short tutorial walks you through a simple counter project that increments upon request using CUDOS Blast.

  1. Create a new folder for the Counter project and initialise Blast.
mkdir Counter
cd Counter
blast init
Success! Sample project initialized in /Users/username/projects/myCudosDapp
  1. Open the project in your preferred IDE

Explore your project​

When you open the project you see something similar to below:

Project contents

Let's walk through each section.

Workspaces​

Inside the contracts folder are alpha and beta folders. These are 2 example workspaces to use if one contract depends on another for example.

Let's enter the alpha folder.

/src directory​

The /src directory contains the smart contract source code in different files.

  1. src/contract.rs - This contains the main smart contract logic and is where the functions instantiate(), execute() and query() are implemented.

  2. src/state.rs - This defines how the smart contract state data is represented and how it will be stored.

  3. src/msg.rs - This is where different types of messages and responses the smart contract can receive and return are defined.

  4. src/error.rs - This is where the different error types are defined that can be returned by the smart contract.

  5. src/lib.rs is where any previous modules are exposed and made accessible.

/scripts directory​

The /scripts directory contains sample scripts

  1. deploy.js - This is a sample script to deploy a compiled contract to the blockchain.

  2. interact.js - This is a sample script to interact with your deployed contract on the blockchain.

/tests directory​

The /tests directory contains sample testing scripts

blast.config.js file​

The blast.config.js is where connections and contract deployments can be configured.

cargo.toml file​

The cargo.toml file must be at the root of the project in order to compile. An artifacts folder is generated after compilation.

State.rs - This is the starting state​

Open /src/state.rs

The starting template has the following state:

a singleton struct State containing:

  • a 32-bit integer (count)

  • an address (owner) a segwit address

In addition, the derive attribute is applied to implement some useful traits:

Serialize: provides serialization Deserialize: provides deserialization Clone: makes our struct copyable Debug: enables our struct to be printed to string PartialEq: gives us equality comparison JsonSchema: auto-generates a JSON schema for us

Msg.rs - InstantiateMsg​

Open /src/msg.rs

use schemars::JsonSchema;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, JsonSchema)]
pub struct InstantiateMsg {
    pub count: i32,
}

This is the message received when an address seeks to instantiate a contract with MsgInstantiateContract. The message provides the contract with an initial configuration and state.

  1. src/contract.rs contains the main smart contract logic and is where the functions instantiate(), execute() and query() are implemented.

Now, we understand the contract, let's compile it.