Quickstart

This section is aimed at newcomers to LIGO and Tezos smart contracts. In this tutorial, we will go through the following steps:

• Writing a simple contract
• Testing the contract
• Deploying the contract to Tezos

Before you start

• Install LIGO on your computer as described in Installation. You can also use the Online IDE but these instructions are for working with LIGO locally.

• Select a syntax. You can use JsLIGO for a JavaScript-like syntax or CameLIGO for an OCaml-like syntax.

  This page provides instructions for both syntaxes. To show the instructions for your syntax, select it under "Syntax Preference" at the top left of the page.

• Optional: Install the IDE plugin for your IDE.

What is a smart contract?

LIGO is a domain-specific language for writing smart contracts on the Tezos blockchain. A smart contract is a piece of code stored on a blockchain. It contains a set of instructions and rules to trigger them. After it is deployed, it becomes immutable, but a user can trigger the execution of the code without modifying it.

A smart contract is composed of three elements:

• Its balance: a contract is a kind of Tezos account, and can receive and send tez tokens
• Its storage: data that is dedicated to and can be read and written by the contract
• Its code: one or more entrypoints, which are a kind of function that can be called either from outside the chain or from other contracts

For more information about smart contracts on Tezos, see Smart contracts on docs.tezos.com.

Writing the smart contract code

These instructions walk you through creating a contract that acts as a counter. It stores a single integer and provides entrypoints that allow users to pass an integer to add or subtract from the current value of the counter.

The only way to change the integer in storage is through these entrypoints. That illustrates how you can store data in a smart contract and enforce specific rules about how that data can change.

Follow these steps to write the code for the contract:

1. On your computer, create a folder to store the contract file, such as ligo_tutorial.

2. Create a file with the extension .jsligo, which indicates JsLIGO code, such as counter.jsligo.

3. In any code or text editor, add this code to the file:

   type storage = int;

   type return_type = [list<operation>, storage];

   This code defines two data types:

   • A type that represents the storage for the contract. In this case, the contract stores an integer, but contracts can define more complex data types to store more data.
   • A type that represents what the contract entrypoints return. LIGO entrypoints always return a list of operations to run after the entrypoint completes and the new state of the storage.

4. Add an entrypoint named add that accepts an integer as a parameter and adds it to the storage value:

   @entry

   const add = (n : int, storage : storage) : return_type => [[], storage + n];

   These lines create a function and annotate it with @entry, which indicates that it is an entrypoint that users can call. Contracts can also include internal functions that are not annotated.

   The function accepts an integer and the current state of the storage as parameters. All entrypoints receive the storage state as their final parameter. The function returns an empty list of operations to run next and the new state of the storage, which in this case is the current integer in storage plus the integer that the caller passed.

5. Similarly, add an entrypoint named sub that accepts an integer and subtracts it from the storage value:

   @entry

   const sub = (n : int, storage : storage) : return_type => [[], storage - n];

The complete contract looks like this:

type storage = int;

type return_type = [list<operation>, storage];

@entry

const add = (n : int, storage : storage) : return_type => [[], storage + n];

@entry

const sub = (n : int, storage : storage) : return_type => [[], storage - n];

That's all that is necessary for a very simple LIGO smart contract.

Trying out the contract

To make sure the contract works as intended, you can use the run dry-run command to simulate a call to one of its entrypoints. For example, to simulate a call to the add entrypoint, pass the file name, the entrypoint and parameter, and the current state of the storage, as in this example:

ligo run dry-run counter.jsligo 'Add(3)' '5'

This command sets the initial storage value to 5 and passes 3 to the add entrypoint. Note that the function name in the code starts with a lower-case letter but the run dry-run command uses entrypoint names that start with an upper-case letter. The result is the return value of the entrypoint, which includes an empty list of operations to run next and the new value of the storage:

( LIST_EMPTY() , 8 )

This way you can test entrypoints manually with different storage states.

Testing the contract

Testing contracts is critical because their code cannot be changed after deployment. For a more powerful way to test contracts than the run dry-run command, you can include automated tests in the contract code.

Follow these steps to add an automated test to the contract:

1. In your contract file, wrap the existing code in a namespace:

   namespace Counter {

   type storage = int;

   type return_type = [list<operation>, storage];

   @entry

   const add = (n : int, storage : storage) : return_type => [[], storage + n];

   @entry

   const sub = (n : int, storage : storage) : return_type => [[], storage - n];

   };

   Namespaces in JsLIGO provide a scope to the identifiers (names of types, functions, variables, etc.) to prevent collisions between them. You can access identifiers that are within a namespace with dot notation, as in <module>.<identifier>.

2. At the end of the file, outside of the namespace, add a function named test_add:

   const test_add = (() => {

   }) ()

3. Inside the function, add code to originate (deploy) the contract to the test environment:

   const initial_storage = 10 as int;

   const orig = Test.Next.Originate.contract(contract_of(Counter), initial_storage, 0tez);

   This command simulates deploying the contract, setting its initial storage to 10, and setting its initial balance to 0 tez.

4. Add code to call the add entrypoint and pass the value 32:

   Test.Next.Contract.transfer_exn(Test.Next.Typed_address.get_entrypoint("add", orig.taddr), 32 as int, 0tez);

5. Add code to verify that the new value of the storage is correct:

   return Assert.assert(Test.Next.Typed_address.get_storage(orig.taddr) == initial_storage + 32);

   The complete code looks like this:

   namespace Counter {

   type storage = int;

   type return_type = [list<operation>, storage];

   @entry

   const add = (n : int, storage : storage) : return_type => [[], storage + n];

   @entry

   const sub = (n : int, storage : storage) : return_type => [[], storage - n];

   };

   const test_add = (() => {

   const initial_storage = 10 as int;

   const orig = Test.Next.Originate.contract(contract_of(Counter), initial_storage, 0tez);

   Test.Next.Contract.transfer_exn(Test.Next.Typed_address.get_entrypoint("add", orig.taddr), 32 as int, 0tez);

   return Assert.assert(Test.Next.Typed_address.get_storage(orig.taddr) == initial_storage + 32);

   }) ()

6. Run this command to run the test:

   ligo run test counter.jsligo

The output shows that the test ran successfully:

Everything at the top-level was executed.

- test_add exited with value ().

Compiling the contract

Tezos runs contracts in the Michelson stack-based language, so you must compile your contract from LIGO to Michelson. The process also looks for errors in the LIGO code.

Run this command to compile the contract:

ligo compile contract counter.jsligo -m Counter -o counter.tz

The command writes the output of the compilation to the file counter.tz. The compiled Michelson contract looks like this:

{ parameter (or (int %sub) (int %add)) ;

storage int ;

code { UNPAIR ; IF_LEFT { SWAP ; SUB } { ADD } ; NIL operation ; PAIR } }

If you see any errors, make sure your code looks like the code in the previous section.

Setting up the Octez client and a local wallet

The Octez client is a command-line tool that lets you send transactions to Tezos, including deploying and calling smart contracts. These instructions show how to install the client, connect it to the Ghostnet test network, and get some tez tokens to pay transaction fees.

The Ghostnet test network is just like the Tezos mainnet, so you can use it to try out your contracts in a live environment before you deploy them to mainnet.

1. Install the Octez client, which sends transactions to Tezos. (The Octez suite includes many programs, but for now all you need is the Octez client.)

   • For Ubuntu, Windows WSL, and Linux distributions that use apt, run these commands:

     REPO="ppa:serokell/tezos"

     sudo add-apt-repository -y $REPO && sudo apt-get update

     sudo apt-get install -y tezos-client

   • For Fedora and Linux distributions that use Copr, run these commands:

     REPO="@Serokell/Tezos"

     dnf copr enable -y $REPO && dnf update -y

     dnf install -y tezos-client

   • For MacOS, use brew:

     brew tap serokell/tezos-packaging-stable https://github.com/serokell/tezos-packaging-stable.git

     brew install tezos-client

   • For other methods, see https://tezos.gitlab.io/introduction/howtoget.html.

2. Verify that you have at least version 20 of the Octez client by running octez-client --version and verifying that the version is at least 20.0.

3. Set the Octez client to use the Ghostnet test network:

   • If you just installed Octez for the first time, run this command:

     octez-client -E https://rpc.ghostnet.teztnets.com config init

   • If you already had Octez installed, run this command:

     octez-client -E https://rpc.ghostnet.teztnets.com config update

4. Verify that you are using Ghostnet by running octez-client config show and verifying that the endpoint field shows https://rpc.ghostnet.teztnets.com, as in this example:

   { "base_dir": "/Users/me/.tezos-client",

   "endpoint": "https://rpc.ghostnet.teztnets.com", "web_port": 8080,

   "confirmations": 0 }

5. Optional: Disable the warning message about using a test network by running this command:

   export TEZOS_CLIENT_UNSAFE_DISABLE_DISCLAIMER=y

6. In the Octez client, create a wallet by running this command:

   octez-client gen keys local_wallet

7. Get your account's address by running this command:

   octez-client show address local_wallet

   The Octez client prints the address of the new wallet in the hash field. The wallet address begins with tz1, as in this example:

   Hash: tz1dW9Mk...........H67L

   Public Key: edp.............................bjbeDj

   You need the wallet address to send funds to the wallet, to deploy the contract, and to send transactions to the contract.

8. Copy your account's address, which starts with tz1.

9. In a web browser, go to the Ghostnet faucet at https://faucet.ghostnet.teztnets.com/.

10. Paste your address into the "Fund any address" field and send some tez to your account. 20 tez is enough to start with, and you can always return to the faucet for more.

11. Verify that your account has tez by running this command:

    octez-client get balance for local_wallet

Now you have an account and funds that you can use to work with Tezos.

Deploying the contract

To deploy (or originate) the contract you need:

• The compiled Michelson code of the contract
• The starting value for the contract storage, compiled as a Michelson expression
• A small amount of tez tokens to pay the transaction fee

1. Get the compiled code of the contract by running this command, where [FILENAME] is the name of your LIGO file.

   ligo compile contract [FILENAME] -m Counter -o counter.tz

2. Get the compiled value of the contract storage by running this command:

   ligo compile storage -m Counter [FILENAME] '0'

   You can put any integer value for the initial storage value as the last parameter in this command.

   The result is the compiled value of the integer in Michelson, which is the same as it is in LIGO. In this case the LIGO storage value maps 1:1 to its Michelson representation. More complex data types like records and maps look different in Michelson than in LIGO.

3. Deploy the contract by running this command, putting the initial storage value in the --init argument:

   octez-client originate contract counter \

   transferring 0 from local_wallet \

   running counter.tz \

   --init 5 --burn-cap 0.5

   This command deploys the contract to the currently selected Tezos network. It includes these parts:

   • It uses the Octez client originate contract command to originate the contract and assigns the local name counter to the contract
   • It includes 0 tokens from your wallet with the transaction, but the --burn-cap argument allows the transaction to take up to 0.1 XTZ from your wallet for fees.
   • It sets the initial value of the contract storage with the --init argument.

   If the contract deploys successfully, Octez shows the address of the new contract, as in this example:

   New contract KT1Nnk.................UFsJrq originated.

   The operation has only been included 0 blocks ago.

   We recommend to wait more.

4. Copy the contract address, which starts with KT1.

5. Optional: Run the command octez-client get balance for local_wallet to get the updated balance of your wallet.

6. Verify that the contract deployed successfully by finding it on a block explorer:

   1. Open a Tezos block explorer such as TzKT or Better Call Dev.

   2. Set the explorer to Ghostnet instead of Mainnet.

   3. Paste the contract address into the search field and press Enter.

   4. Go to the Storage tab to see that the initial value of the storage is the integer that you provided.

Now the contract is deployed and unchangeable. Anyone can call its entrypoints to change the storage value.

Calling the contract

You can call the contract from many different Tezos clients, including web applications, block explorers, and the Octez client. To call the contract from the Octez client, pass the entrypoint name and parameter to the octez-client transfer command, as in this example:

octez-client --wait none transfer 0 from local_wallet \

to counter --entrypoint 'add' --arg '5' --burn-cap 0.1

Like the originate contract command, this command takes the address or local name of the contract, an amount of tez to include, and a maximum fee. It also includes the name of the entrypoint and the Michelson-encoded parameter to send to it.

Entrypoints don't return values, so the output shows only that the transaction was added successfully. To verify that the transaction ran, you can check the value of the contract storage, either by looking it up in a block explorer or using the Octez client, as in this example:

octez-client get contract storage for counter

Next steps

Now you have a simple LIGO smart contract and can test it, deploy it, and call it. You can use it as a starting point to write your own contracts and experiment with LIGO.

You can also continue with the Taco shop tutorial to learn more about programming with LIGO.