In this tutorial, you learn how to .... By the end of this tutorial, you will ...
*
## Overview
* TOC
{:toc}
<divclass="uk-card uk-card-default uk-card-body">
<h5>Early Release</h5>
<p>Clarity and its accompanying toolset are in early release. If you encounter issues with or have feature requests regarding Clarity, please create an issue on the <ahref='https://github.com/blockstack/stacks-blockchain/issues'target='_blank'>blockstack/stacks-blockchain</a> repository. To read previous or join ongoing discussions about smart contracts in general and Clarity in particular, visit the <strong><ahref='https://forum.blockstack.org/c/clarity'target='_blank'>Smart Contracts</a></strong> topic in the Blockstack Forum.
</p>
</div>
## Pre-requisites
...
## Step 1:
...
## Where to go next
{:.no_toc}
* <ahref="clarityRef.html">Guide to principals</a>
* <ahref="clarityRef.html">Clarity language reference</a>
In this tutorial, you learn how to use Clarity, Blockstack's smart contracting language inside of a virtual environment. The environment is run using a [Docker](https://www.docker.com/) image. Use this tutorial to get a quick introduction to Clarity and the default Blockstack test environment.
In this tutorial, you learn how to use Clarity, Blockstack's smart contracting language. By the end of this tutorial, you will ...
By the end of this tutorial you will ...
* Have a working Clarity starter project
* Have working test environment to run Clarity smart contracts
* Have access to a set of sample contracts to play with
* Understand basic Clarity language design principles
* Understand basic Clarity language design principles
* Deploy and run your own smart contract
* Understand how to interact with smart contracts
* Understand how to test smart contracts
## Overview
## Overview
@ -28,309 +26,184 @@ By the end of this tutorial you will ...
</p>
</p>
</div>
</div>
## Before you begin (pre-requisites)
## Pre-requisites
The Clarity language goes live with the release of Stacks2.0. Until then, you can run Clarity in a test environment. You run this test environment in a Docker container. Before you begin this tutorial, make sure you have <ahref="https://docs.docker.com/get-docker/"target="_blank">Docker installed on your workstation</a>.
You can verify your Docker installation by running the following in your terminal:
To complete the tutorial, you should have [NodeJS](https://nodejs.org/en/download/) installed on your workstation. You can verify your installation by opening up your terminal and run the following command:
```bash
```shell
docker verion
npm --version
```
```
You should see the version of your Docker engine running on your workstation.
A version should be returned, indicating that NodeJS installed successfully.
## Step 1: Set up the test environment
In this step, you use the [Docker CLI](https://docs.docker.com/engine/reference/commandline/cli/) to pull and run the image on your local workstation.
1. Using your terminal, download the latest [Stacks 2.0 blockchain Docker image](https://hub.docker.com/r/blockstack/stacks-blockchain) from the Docker Hub:
## Step 1: Installing Clarity JS SDK
```bash
In this step, you initialize a starter project for Clarity development:
docker pull blockstack/stacks-blockchain:latest
```
2. Now, you can start the Stack2.0 test environment in your terminal:
1. Using your terminal, run the following command:
```bash
```bash
docker run -it -v $HOME/blockstack-dev-data:/data/ blockstack/stacks-blockchain:latest bash
npm init clarity-dev
```
```
The command opens a bash shell inside the Docker image, so that you can operate in the test environment.
2. After the starter project was loaded up, you are asked to name the starter project. Feel free to hit ENTER to accept the default suggestion.
## Step 2: Review sample contracts
With a test environment running on your workstation, let's have a look at some sample contracts implemented with Clarity.
1. Still inside the bash shell of the Docker image, list the contents of the `sample-contracts` directory.
```bash
```bash
ls sample-contracts/
? Project name (clarity-dev-project)
```
```
This directory contains a set of simple Clarity contracts. Note that all Clarity files have a `.clar` suffix.
Finally, the project dependencies are installed and your project is ready for development.
2. Let's review the contents of `tokens.clar` with the `cat` command.
3. The project is located in a new folder, `clarity-dev-project` by default. Jump into the folder and have a look at the file structure:
```bash
```bash
cat sample-contracts/tokens.clar
cd clarity-dev-project
ls
```
```
You should see the contract source code. Take a few minutes to review the content.
Take note of the `contracts` and `test` folders. The other files are boilerplate to wire up the project.
Clarity is a programming language based on [LISP](https://en.wikipedia.org/wiki/Lisp_(programming_language)). Most notably, Clarity is designed for static analysis, not compiled, and **not** [Turing complete](https://en.wikipedia.org/wiki/Turing_completeness).
## Step 2: Reviewing hello world contract
Let's go through the source code:
Now, let's have a look at a Clarity smart contract and get familiar with the basic language design characteristics.
```cl
1. Still inside the terminal, list the contents of the `contracts/sample` folder.
Notice the program and each statement is enclosed in `()` (parentheses).
The first line defines a map for `tokens` with the account-balance key-value pairs. The `account` key is of the [`principal`](https://docs.blockstack.org/core/smart/clarityref#principal-type) type. Principals represent a spending entity and are roughly equivalent to a Stacks address. The `balance` value is an unsigned integer ([`uint`](https://docs.blockstack.org/core/smart/clarityref#uint-type)). Along with principals and signed/unsigned integers, Clarity supports the following types:
On line 2 and 3, a `get-balance` function is declared as a private function. To create public functions, you would use the `define-public` function. Public functions can be called from DApps, CLIs, or other contracts.
The `get-balance` function returns the value (`balance`) for the key provided (`account`). Using `default-to`, an unsigned integer `0` (note the `u0` literal to differentiate between signed integers) is returned if the account key cannot be found in the `tokens` map.
Let's look at the next method definition. The private method `token-credit!` is defined below. It takes a principal and unsigned integer as input parameters:
On the first line of the method, we see how conditions can be used with the [`if`](https://docs.blockstack.org/core/smart/clarityref#if) statement. The if statement takes a boolean argument and two expressions. The first expression is executed when the boolean argument evalutes true. In this case, [`err`](https://docs.blockstack.org/core/smart/clarityref#int-type) is used to return an error response type with the error message provided.
--> TODO
Variables are created via [`let`](https://docs.blockstack.org/core/smart/clarityref#let) binding, but there is no support for mutating functions like `set`.
Every smart contract has both a data space and code. The data space of a contract may only interact with that contract. This particular function is interacting with a map named `tokens` (defined on line 1). The [`map-set`](https://docs.blockstack.org/core/smart/clarityref#map-set) function sets the value associated with the input key to the inputted value in the `tokens` data map.
In the first `token-transfer` public function, you see that it calls the private `get-balance` function and passes it `tx-sender`. The `tx-sender` is a globally defined variable that represents the current principal.
The final two lines of the program pass a principal, represented by a Stacks address, and an amount to the private user-defined `token-credit` function.
Smart contracts may call other smart contracts using a `contract-call!` function. This ability means that if a transaction invokes a function in a given smart contract, that function is able to make calls into other smart contracts on your behalf. The ability to read and do a static analysis of Clarity code allows clients to learn which functions a given smart contract will ever call. Good clients should always warn users about any potential side effects of a given transaction.
Take a moment to `cat` the contents of the `sample-contracts/names.clar` file.
```bash
```bash
cat sample-contracts/names.clar
ls contracts/sample
````
Which `tokens.clar` function is being called?
## Task 3: Initialize data-space and launch contracts
In this task, you interact with the the contracts using the `clarity-cli` command line.
1. Initialize a new `db` database in the `/data/` directory
```bash
# clarity-cli initialize /data/db
Database created
```
```
You should see a message saying `Database created`. The command creates an SQLlite database. The database is available in the container and also in your workstation. In this tutorial, your workstation mount should, at this point, contain the `$HOME/blockstack-dev-data/db` directory.
This directory contains a hello world Clarity contract. Note that all Clarity files have a `.clar` suffix.
2. Type check the `names.clar` contract.
2. Let's review the contents of `hello-world.clar` with the `cat` command.
You should see the contract source code. Take a few seconds to review the content.
```
Clarity is a programming language based on [LISP](https://en.wikipedia.org/wiki/Lisp_(programming_language)). Most notably, Clarity is designed for static analysis, not compiled, and **not** [Turing complete](https://en.wikipedia.org/wiki/Turing_completeness).
Error (line 11, column 1): use of unresolved contract ''S1G2081040G2081040G2081040G208105NK8PE5.tokens'.
```
This happens because the `names.clar` contract _calls_ the `tokens.clar` contract, and that contract has not been created on the blockchain.
Let's go through the source code. Notice how the program and each statement is enclosed in `()` (parentheses). You'll see that the smart contract consists of two public methods. Starting at the top, let's review line by line:
3. Type check the `tokens.clar` contract, it should pass a check as it does not use the `contract-call` function:
When the `check` command executes successfully and exits with the stand UNIX `0` exit code.
On the first line, a new public method `say-hi` is declared. To create private functions, you would use the `define-private` function. Note that only public functions can be called from outside e.g., through other smart contracts.
4. Generate a demo Stacks address for testing your contract.
The method doesn't take any parameters and simply returns "hello world" using the [`ok`](https://docs.blockstack.org/core/smart/clarityref#ok) response constructor.
This address is used to name your contract at launch time. You can use any existing Stacks address. For this sample, you are going to use the `generate_address` command to create one.
Let's review the second public method, `echo-number`. As opposed to the function before, this takes an input parameter of the type [`int`](https://docs.blockstack.org/core/smart/clarityref#int-type). Along with integer, Clarity supports the following types:
* [tuple](https://docs.blockstack.org/core/smart/clarityref#tuple-type): named fields in keys and values
```bash
The function simply uses the `ok` response and returns the value passed to the method.
# clarity-cli generate_address
SP28Z69HE5H70BVRG4VGKN4SYNVJ1J0417WVCKZWM
## Step 3: Running tests
```
The demo address you generate will be different than the one that appears in this example.
Smart contracts are often developed in a test-driven approach to ensure code quality but also to speed up the development cycle by removing the need to push every change to the blockchain before executing it. We will do the same in this project. In fact, the started project comes with test tooling already set up for you (using [Mocha](https://mochajs.org/)). Let's run the tests and review the results:
5. Add the address to your environment.
1. Still in the project root directory, run the following command:
6. Launch the `tokens.clar` contract and assign it to your `DEMO_ADDRESS` address.
You should see the following response:
You use the `launch` command to instantiate a contract on the Stacks blockchain. If you have dependencies between contracts, for example `names.clar` is dependent on `tokens.clar`, you must launch the dependency first.
Once launched, you can execute the contract or a public method on the contract. Your development database has an instantiated `tokens` contract. If you were to close the container and restart it later with the same mount point and you wouldn't need to relaunch that database; it persists until you remove it from your local drive.
7. Instantiate the `names.clar` contract and assign it to your `DEMO_ADDRESS` address. as well.
Oh, it looks like we see some failed test! That is on purpose - we will implement a new smart contract in the next tutorial! After every increment of the contract, we will run the tests again to ensure we're on the right track. For now, let's have a look at how we can interact with Clarity smart contracts.
The test environment uses a SQLite database to represent a virtual blockchain. You initialized this database when you ran this earlier:
## Step 4: Interacting with contracts
```bash
Tests are located in the `test` folder, let's have a look at the tests associated with the `hello-world.clar` file.
clarity-cli initialize /data/db
```
As you work the contracts, data is added to the `db` database because you pass this database as a parameter, for example:
The database exists on your local workstation and persists through restarts of the container. You can use this database to explore the transactional effects of your Clarity programs. The SQLite database includes a single `data_table` and a set of `marf` structures.
Take a few seconds to review the contents of the file. You should ignore the test setup methods and focus on the most relevant parts related to Clarity.
While not required, you can install SQLite in your local environment and use it to examine the data associated with and impacted by your contract. For example, this what the `data_able` contains after you initialize the `tokens` contract.
<imgsrc="../images/sqlite-contract.png"alt="">
The `marf` directory defines a data structure that handles key-value lookups in the presence of blockchain forks. These structures are not intended for use in debugging, they simply support the implementation.
## Task 5: Execute a public function
In this section, you use the public `mint!` function in the `tokens` contract to mint some new tokens.
Note that we're importing modules form the `@blockstack/clarity` package:
1. Get the current balance of your new address.
```js
import { Client, Provider, ProviderRegistry, Result } from "@blockstack/clarity";
This command uses the private `get-balance` function in the `tokens` contract and pipes the result to the `eval` subcommand. The `eval` subcommand lets you evaluate both public and _private_ functions of a contract in read-only mode.
### Initiliazing a client
2. Try minting some tokens and sending them to an address we'll use for our demo.
```bash
At the test start, we are initializing contract instance `helloWorldClient` and a provider that forwards commands to the Rust CLI in order to interact with the Stack2.0 blockchain.
helloWorldClient = new Client("SP3GWX3NE58KXHESRYE4DYQ1S31PQJTCRXB3PE9SB.hello-world", "sample/hello-world", provider);
Program executed successfully! Output:
100000
```
```
## Task 6: Spend tokens by registering a name
Take a look at the client initialization. It requires a contract id and name in the following format: `{contract_id}.{contract_name}`. The second parameter indicates the location of the smart contract file, without the `.clar` suffix. By default, the location is assuming to be relative to the `contracts` folder.
Now, let's register a name using the `names.clar` contract. Names can _only_ be integers in this sample contract, so you'll register the name 10 in this environment.
1. Compute the hash of the name we want to register.
### Checking syntax
You'll _salt_ the hash with the salt `8888`:
Next, we check the contract for valid syntax with:
Note that the `checkContract()` method returns a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise). The `await` command makes sure JavaScript is not executing the next lines until the contract check completes.
```
### Deploying contract
0xb572fb1ce2e9665f1efd0994fe077b50c3a48fde
```
2. Preorder the name using the _execute_ command:
Further down in the file, you find a contract deployment:
This executes the public `preorder` function defined in the `names.clar` contract. The function reserves a name by paying the name fee (in this case, 1000 tokens).
### Run public methods
3. Check the demo address' new balance:
Finally, you will find snippets that call the public `say-hi` method of the contract:
4. Register the name by executing the _register_ function:
As you see, smart contract calls are realized through query definitions. The `createQuery` method defines the name and arguments passed to the smart contract function. With `submitQuery`, the method executed and the response is wrapped into a `Result` object. To obtain the readable result, we use the `unwrapString` method, which should return `hello world`.
```bash
Now, review the last test `should echo number` on your own and try to understand how arguments are passed to the `echo-number` smart contract.
Alex Graebe
5 years ago