Developing and deploying Tezos smart contracts

Tezos is one of the oldest smart contract blockchains, with Ethereum being the very first.

While Ethereum is a popular choice among developers for developing and deploying smart contracts, its applications are not very scalable due to high fees and slow transactions. In contrast, Tezos applications are very efficient and inexpensive to set up.

In this guide, you will learn how to develop and deploy smart contracts in Tezos with SmartPy CLI. We will cover:

• What is Tezos?
  • Tezos vs. Ethereum: A comparison chart
• What is SmartPy?
• What are smart contracts?
• Getting started with SmartPy CLI
• Setting up tezos-client
• Developing a Tezos smart contract with SmartPy
• Testing the Tezos smart contract
• Compiling the smart contract to Michelson
• Deploying the Tezos smart contract
• Interacting with the deployed smart contract

You can get the final project’s code in this GitHub repo.

Prerequisites

To follow along with this article, you need to be familiar with the Tezos blockchain. Your knowledge doesn’t have to be in-depth.

Knowledge of the Ethereum blockchain is not required, but it helps a lot.

What is Tezos?

Tezos is a blockchain network and a smart contract platform that is built to be adaptive through its governance model and self-upgrading ability.

While Tezos and Ethereum are similar blockchains that support smart contracts and DApp development, they are different in several ways. The Tezos vs. Ethereum table below shows some of the differences between the two networks.

Tezos vs. Ethereum: A comparison chart

What is SmartPy?

SmartPy is a tool that allows you to build smart contracts easily on the Tezos blockchain.

You write contracts in SmartPy using Python. If you’re already familiar with Python, you don’t have to learn a new smart contract programming language.

SmartPy comes in two other variants that use other syntaxes: SmartTS, which uses TypeScript, and SmartML, which uses OCaml.

SmartPy compiles Python scripts to Michelson. Michelson is a low-level programming language for smart contracts in Tezos. SmartTS and SmartML can also be compiled using the SmartPy tool.

What are smart contracts?

Smart contracts are programs that you can build, deploy, and execute on a blockchain network. You don’t need to own a node on the network before deploying your smart contract.

With smart contracts, you can build applications accessible to all devices without owning or maintaining a server. These fully decentralised applications require little or no maintenance.

Smart contracts use the full potential of blockchains, allowing you to execute programs on the chain as well as to interact with the chain itself. You can hold or transfer tokens and access specialised functionality on the blockchain with a smart contract.

Getting started with SmartPy CLI

To install SmartPy CLI, run the command below:

$ bash <(curl -s https://smartpy.io/cli/install.sh)

This command creates a smartpy-cli directory in home with this tree structure:

smartpy-cli
├── browser.py
├── node_modules/
├── originator.js
├── package.json
├── package-lock.json
├── __pycache__/
├── smart.css
├── smart.js
├── smartpyc.js
├── smartpyc.py
├── smartpyio.py
├── smartpy.py
├── SmartPy.sh
├── smarttop/
├── smart-ts-cli.js
├── templates/
├── theme.js
└── typography.css

To confirm the installation, run the following:

$ ~/smartpy-cli/SmartPy.sh --version

As an extra step to make SmartPy.sh easily accessible, create an alias by copying the below into your .bashrc file or related profile file:

$ alias smartpy="$HOME/smartpy-cli/SmartPy.sh"

Now you can use:

$ smartpy --version

Instead of:

$ ~/smartpy-cli/SmartPy.sh --version

Setting up tezos-client

This guide uses tezos-client to interact with a deployed smart contract. To install tezos-client, run one of the commands below, depending on whether you are using a Mac or Linux operating system:

# Mac
$ brew tap serokell/tezos-packaging-stable https://github.com/serokell/tezos-packaging-stable.git
$ brew install tezos-client

# Linux
$ wget https://github.com/serokell/tezos-packaging/releases/latest/download/tezos-client
$ chmod +x tezos-client
$ mkdir -p $HOME/.local/bin
$ mv tezos-client $HOME/.local/bin
$ echo 'export PATH="$HOME/.local/bin:$PATH"' >> $HOME/.bashrc
$ source $HOME/.bashrc

Note that if you are using Windows, you need to install a Linux distro with wsl and run the Linux installation.

After installing tezos-client, you need to set it up. Start by running the command below:

$ tezos-client --endpoint https://jakartanet.ecadinfra.com config update

This guide uses the Jarkatanet testnet to deploy and interact with a smart contract. The above command connects tezos-client to the Jakartanet testnet through the node https://jakartanet.ecadinfra.com on the network.

Before you perform any operation with tezos-client, you need to connect an account. Tezos provides Faucet accounts that allow you to interact with the network for free.

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You need to visit the Jakartanet Faucet website and download the Faucet file. After doing that, open the download folder in your terminal and run this command:

$ tezos-client activate account faucet with ./jakartanet.json

The command activates the Faucet account in your tezos-client and gives it an alias faucet. To check the balance for this account, open the jakartanet.json file, copy the value of pkh, then run this command:

$ tezos-client get balance for <address>

Replace <address> with the pkh value that you copied.

Note that Tezos Faucet accounts are publicly available to everyone and have a limited amount of Tez tokens, so you have to regulate your usage.

Developing a Tezos smart contract with SmartPy

To begin creating our example smart contract, create a new store_text.py file and copy the below into it:

import smartpy as sp

class StoreText(sp.Contract):
    def __init__(self, value):
        self.init(text = value)

    @sp.entry_point
    def replace(self, params):
        self.data.text = params.text

    @sp.entry_point    # Note: the spaces before "@"
    def append(self, params):
        self.data.text += params.text

Here’s how the above contract works, piece by piece:

First, we imported the smartpy library:

import smartpy as sp

Then, we defined a class that extends sp.Contract:

class StoreText(sp.Contract):

Lastly, we defined a few items within the smart contract; first, a constructor to initialise text:

    def __init__(self, value):    # Note: the spaces before "def"
        self.init(text = value)

Second, an entry point to replace the value of text:

    @sp.entry_point    # Note: the spaces before "@"
    def replace(self, params):
        self.data.text = params.text

Third, an entry point to append a string to text:

    @sp.entry_point    # Note: the spaces before "@"
    def append(self, params):
        self.data.text += params.text

Next, let’s take a look at how to test the smart contract.

Testing the Tezos smart contract

Smart contracts that are deployed to Tezos cannot be changed or removed. This can be a problem because there could be errors in the contract, and errors could lead to costly mistakes and the loss of funds.

SmartPy gives you the ability to easily test your contract before deploying. Testing the contract doesn’t require any tokens or a wallet account to run. All you need to do is open the store_text.py file and copy the below below it:

@sp.add_test(name = "StoreText")
def test():
  scenario = sp.test_scenario()
  contract = StoreText("Hello")
  scenario += contract

  scenario.verify(contract.data.text == "Hello")

  contract.replace(text = "Hi")
  contract.append(text = ", there!")
  scenario.verify(contract.data.text == "Hi, there!")

Here’s how the snippet works. First, we registered a the test function as a test script:

@sp.add_test(name = "StoreText")

Then, we defined the test function:

def test():

In the remaining lines, we created a test scenario:

  scenario = sp.test_scenario()

Initialized the contract with "Hello":

  contract = StoreText("Hello")

Added the contract instance to the scenario:

  scenario += contract

Verified that the contract’s text value is "Hello":

  scenario.verify(contract.data.text == "Hello")

Called the replace and append entry points:

  contract.replace(text = "Hi")
  contract.append(text = ", there!")

And finally, verified that the contract’s text value is now "Hi, there":

  scenario.verify(contract.data.text == "Hi, there!")

After adding the test, save the file and run this command:

$ ~/smartpy-cli/SmartPy.sh test store_text.py ./test-output

If the test is successful, the compiler won’t throw an error message.

Compiling the smart contract to Michelson

Before you deploy your smart contract, you need to compile it to Michelson. As mentioned earlier, Michelson is a low-level programming language used for smart contracts on the Tezos blockchain.

To compile store_text.py, run the following:

$ ~/smartpy-cli/SmartPy.sh compile message.py ./output

If it compiled successfully, you should see an output folder like the one below:

output/
├── scenario.json
├── script_init.py
├── script_pure.py
└── storeMessage/
    ├── log.txt
    ├── step_000_cont_0_contract.json
    ├── step_000_cont_0_contract.py
    ├── step_000_cont_0_contract.tz
    ├── step_000_cont_0_sizes.csv
    ├── step_000_cont_0_storage.json
    ├── step_000_cont_0_storage.py
    ├── step_000_cont_0_storage.tz
    └── step_000_cont_0_types.py

The output directory contains all the files necessary to deploy the smart contract.

Deploying the Tezos smart contract

To deploy store_text.py, open the output/storeMessage folder in the terminal and run the command below:

$ ~/smartpy-cli/SmartPy.sh originate-contract --code step_000_cont_0_contract.json --storage step_000_cont_0_storage.json --rpc https://jakartanet.ecadinfra.com

[INFO] - Using RPC https://jakartanet.ecadinfra.com/...
[INFO] - Contract KT1………………CAjjW originated!!!

Here’s is how the command works:

• originate-contract tells tezos-client to deploy (“originate”) a contract
• --code step_000_cont_0_contract.json points to the compiled contract file
• --storage step_000_cont_0_storage.json points to the compiled storage file
• --rpc https://jakartanet.ecadinfra.com points to an RPC node on the network you are deploying to

Tezos smart contracts usually involve two components: the storage and the contract. The storage holds the data that the contract stores, and the contract holds the logic of the smart contract.

Note that you can deploy the contract with any of the contract or storage compilations. They just have to be the same file extension when you are using the command.

By default, if you’re deploying on a testnet, the compiler will use a Faucet account. If you are deploying to the mainnet or you want to use your wallet account, add the --private-key flag followed by the account’s private key.

Interacting with the deployed smart contract

Before interacting with the deployed smart contract, you need to know how the contract currently looks. To do that, open the SmartPy Explorer in your browser and follow these steps:

1. Navigate to “Alternative Nodes”
2. Paste the contract’s address in the “Contract” input
3. Under “Explore on a Specific Node,” switch from mainnet to jakartanet
4. Paste the RPC URL https://jakartanet.ecadinfra.com to the text box
5. Click on “Explore on a Specific Node”

When the contract data has appeared, the text storage should display as “Hello, There!”

Now that you know the contract’s text, you can change it to “Hi, There!” by calling the replace entrypoint with this command:

$ tezos-client transfer 0 from faucet to <contract-address> --entrypoint replace --arg '"Hi, There!"'

If the command was successful, when you refresh the explorer, the storage should now display “Hi, There!”

Note that you must replace <contract-address> with the address of the deployed contract before running the command.

Conclusion

This article covers the process of building smart contracts on Tezos with SmartPy. Building smart contracts allows you to take full advantage of the blockchain network to build decentralised applications and organisations.

I hope this article helped you understand the process of building smart contracts on Tezos. If you’d like to read more about smart contracts, check out this article about smart contract mistakes to avoid.

Thanks for reading! And have a nice day.Developing and deploying Tezos smart contracts

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