Fetch Network
Jenesis
Working with contracts
How to add contract templates
JenesisSmart contractsBlockchainTemplatesTutorial

How to add contract templates

Introduction

Once you have successfully created your project ↗ī¸, you can add contract templates.

A contract template is a pre-defined, reusable blueprint or pattern for creating a smart contract in a blockchain environment. It provides a structured starting point with predefined functionalities, variables, and logic that can be customized to suit specific use cases.

ℹī¸

A contract template is a specific implementation that can be added to a project. These templates serve as a foundation for creating contracts by providing pre-configured settings, initial code, and common functionalities. They streamline the process of developing contracts by offering a structured starting point that developers can build upon. By using contract templates, developers can save time and effort in setting up the basic structure and functionalities of their contracts, allowing them to focus on customizing and implementing the specific features required for their use case.

Overview

If you want to add a template to a contract, you first need to navigate into your project's directory and run the following command:

jenesis add contract <template> <contract_name>

You can find all the contract templates available in Jenesis Templates ↗ī¸ (opens in a new tab) GitHub repository. As for an overview, the available templates are the following:

Example: CW-20 basic template for fungible token contract

The cw20-base template is designed for creating CW-20 tokens on the Fetch.ai blockchain. CW-20 tokens are a standard interface for fungible tokens. This template provides a solid starting point for developers looking to create their own custom CW-20 tokens, complete with essential functionalities like transfers, approvals, and querying balances.

The steps needed to add the cw20-base template with the name my_token are provided below:

jenesis add contract cw20-base my_token

If you need multiple deployments of the same contract, you can use the --deployments or -d flag to specify multiple deployments and name them:

jenesis add contract <template> <contract_name> [--deployments <deployments>]

Jenesis will add the deployments to all profiles for the specified contract.

In the example below, token_1 and token_2 deployments have been added. This will allow you to deploy my_token contract with two different configurations. You can add as many deployments as we wish:

jenesis add contract cw20-base my_token -d token_1 token_2

If no deployments are selected when adding a contract, the default deployment name will be equal to the contract name.

The add contract command will add a contract template to our jenesis project inside contracts/my_token/ folder. It will also update the jenesis.toml configuration file with the contract information:

[profile.testing.contracts.token_1]
name = "token_1"
contract = "my_token"
network = "fetchai-testnet"
deployer_key = ""
init_funds = ""
 
[profile.testing.contracts.token_2]
name = "token_2"
contract = "my_token"
network = "fetchai-testnet"
deployer_key = ""
init_funds = ""
 
[profile.testing.contracts.token_1.init]
 
[profile.testing.contracts.token_2.init]

The deployer_key field can be manually specified. You can choose any private key locally available to deploy any specific contract. You can also leave this field empty since the deploy command has an optional argument to deploy all contracts inside a specified profile with the same key, overriding this deployer_key argument in the jenesis.toml file. Checkout the deploy contracts ↗ī¸ guide for more information.

Finally, the init section contains the parameters needed in the instantiation message for this contract to be deployed. The required parameters are taken from the schema file inside the contracts directory. Since this contract template doesn't include a schema, it will be generated when compiling ↗ī¸ the my_token contract loading the init fields to the jenesis.toml file. You will need to manually add the values for these parameters in their correct variable type, which are listed on the schema file. For this my_token contract, you need to fill the init fields for each deployment after compiling ↗ī¸.

Below, we can find an example for this:

[profile.testing.contracts.token_1.init]
decimals = 6
name = "my_token_name"
symbol = "SYMBOL"
initial_balances = [{ address = "fetch1d25ap9danl4726uk2nt307y630v87h3h2vq6pl", amount =  "5000"}]

[profile.testing.contracts.token_2.init]
decimals = 6
name = "my_token_name_2"
symbol = "SYMBOL"
initial_balances = [{ address = "fetch1d25ap9danl4726uk2nt307y630v87h3h2vq6pl", amount =  "2000"}]

If your contract requires nested instantiation messages, you may add fields following this structure:

[profile.testing.contracts.example-nested-contract.init]
price = {amount = 1000, denom = DLS}
info = {performance = {max_speed = 200, unit = kph}, fuel = {consumption = 7, unit = kmpl}}
⚠ī¸

Before editing the jenesis.toml configuration file with the desired deployer_key and init parameters, make sure to first compile ↗ī¸ your contract. All configuration parameters will restart every time a contract is compiled if the schema has changed

You can also add contracts manually by copying and pasting the contract directory from another project you may have. However, they would need to follow the same directory structure as the starter ↗ī¸ (opens in a new tab) template.

When adding a contract manually, you need to update the jenesis.toml file with the contract information by running the following command:

jenesis update

The update command will automatically detect which contract is missing in the jenesis.toml configuration file by revising the contracts directory.

Add contract deployments

You can also add further deployments for a given contract by specifying the contract name and the deployment name.

If you want to add a third token called token_3 using my_token contract, you can run:

jenesis add deployment my_token token_3

This will automatically create another deployment entry called token_3.

Attach deployed contracts

If you add a contract into the project's contract folder that has already been deployed in the network, you can attach the deployment to your project for future interaction using the attach command.

You can add a deployment to your project by running the following command:

jenesis add contract cw20-base my_token -d token_1

Then, you would need to compile the contract:

jenesis compile

You can also attach the contract. In this case, you will need to specify the deployment's name and address. You can optionally specify the profile where you wish to insert the contract into. If this is not specified, the deployment will be attached to the default profile, which is the first profile created in our project, unless the default settings are manually changed:

jenesis attach token_1 fetch18xs97q6h9zgh4sz730a42pp0dqa9sh4eef7eutfkv69q3v2y3x8s72pkua

This will add the relevant deployment information into a jenesis.lock file and you will now be able to interact with token_1 using contract interactions ↗ī¸.

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