Hello, World! revisited

Before you begin

• You have a GitHub account and can run git commands.
• You have installed the Pact programming language and command-line interpreter.
• You have installed the kadena-cli package and have a working directory with initial configuration settings.
• You have a local development node that you can connect to that runs the chainweb-node program, either in a Docker container or on a physical or virtual computer.

Get the starter code

1. Open a terminal shell on your computer.

2. Clone the pact-coding-projects repository by running the following command:

   git@github.com:kadena-docs/pact-coding-projects.git

   git@github.com:kadena-docs/pact-coding-projects.git

3. Change to the 00-hello-world directory by running the following command:

   cd pact-coding-projects/00-hello-world

   cd pact-coding-projects/00-hello-world

4. Open the hello-world.pact file in your code editor.

   ;;;; "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;----------------------------------------------------------------------- (module helloWorld GOVERNANCE    "You can also embed comments in smart contracts by using quoted strings."     (defcap GOVERNANCE () true)      (defun say-hello(name:string)        (format "Hello, {}! ~ from Kadena" [name])    ))

   ;;;; "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;----------------------------------------------------------------------- (module helloWorld GOVERNANCE    "You can also embed comments in smart contracts by using quoted strings."     (defcap GOVERNANCE () true)      (defun say-hello(name:string)        (format "Hello, {}! ~ from Kadena" [name])    ))

   A few things you should note about this starter code:

   • The module being defined is named helloWorld.
   • Every module is governed by either a keyset or a capability. In this example, the GOVERNANCE capability is used to control access to the module. This capability must evaluate to true to grant access.
   • The defun reserved keyword signals the start of a function definition. In this example, the function being defined is named say-hello and the function takes one variable, name, with a data type of string.
   • The say-hello function uses the built-in format function that allows you to format messages using a placeholder and a variable or a specified value. The curly braces ({}) indicate the location of the value to be inserted and the [name] is the variable to be inserted in place of the curly braces ({}).

   To learn more, see the following topics:

   • Syntax and keywords
   • General built-in functions

Load and test the module

1. Add a call to the say-hello function at the bottom of the hello-world.pact file in your code editor.

   ;;;; "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;----------------------------------------------------------------------- (module helloWorld GOVERNANCE    "You can also embed comments in smart contracts by using quoted strings."     (defcap GOVERNANCE () true)      (defun say-hello(name:string)        (format "Hello, {}! ~ from Kadena" [name])    )) (say-hello "Pistolas") 

   ;;;; "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;----------------------------------------------------------------------- (module helloWorld GOVERNANCE    "You can also embed comments in smart contracts by using quoted strings."     (defcap GOVERNANCE () true)      (defun say-hello(name:string)        (format "Hello, {}! ~ from Kadena" [name])    )) (say-hello "Pistolas") 

2. Open a terminal shell on your computer.

3. Start the Pact interpreter by running the following command:

   pact

   pact

   After running this command, the terminal displays the pact > prompt:

   pact >

   pact >

4. Copy and paste the helloWorld module code into the terminal with the pact > prompt, then press Return on the keyboard to load the module.

   You should see that the module loads and the call to the say-hello function is executed with output similar to the following:

   "Loaded module helloWorld, hash fsYJQuzCtzdocWkgjS9yXFz6WAJlV0Aor1RmWhyfgc0"pact> pact> (say-hello "Pistolas")"Hello, Pistolas! ~ from Kadena"

   "Loaded module helloWorld, hash fsYJQuzCtzdocWkgjS9yXFz6WAJlV0Aor1RmWhyfgc0"pact> pact> (say-hello "Pistolas")"Hello, Pistolas! ~ from Kadena"

5. Exit the Pact interpreter by pressing control-d on the keyboard.

Create a hello-world.repl file

1. Create a new file named hello-world.repl file in your code editor.

2. Use the built-in (begin-tx) and (commit-tx) functions to define a transaction that loads the hello-world.pact file:

   (begin-tx)  (load "hello-world.pact")(commit-tx)

   (begin-tx)  (load "hello-world.pact")(commit-tx)

3. Open a terminal shell and execute the hello-world.repl file by running the following command:

   pact --trace hello-world.repl

   pact --trace hello-world.repl

   Notice that you are executing the file in a terminal shell and not in the Pact command-line interpreter. This command executes the functions defined in the hello-world.repl file and displays output in the terminal similar to the following:

   hello-world.repl:1:0:Trace: Begin Tx 0hello-world.repl:2:0:Trace: Loading hello-world.pact...hello-world.pact:15:0:Trace: Loaded module helloWorld, hash Nci-2EJkgvvHnVLyfOJG-WKGuQ6-tLAYWRYVGPGW2cchello-world.pact:24:0:Trace: Hello, Pistolas! ~ from Kadenahello-world.repl:3:0:Trace: Commit Tx 0Load successful

   hello-world.repl:1:0:Trace: Begin Tx 0hello-world.repl:2:0:Trace: Loading hello-world.pact...hello-world.pact:15:0:Trace: Loaded module helloWorld, hash Nci-2EJkgvvHnVLyfOJG-WKGuQ6-tLAYWRYVGPGW2cchello-world.pact:24:0:Trace: Hello, Pistolas! ~ from Kadenahello-world.repl:3:0:Trace: Commit Tx 0Load successful

   To learn more, see the following topics:

   • Testing Pact programs
   • REPL-only functions

Modify the module to store names

1. Copy the hello-world.pact file to create a new file named 2-hello-world.pact file in your code editor.

2. Modify the module code to create a schema and table for storing greeting recipient values and add functions to write and read the value from the table.

   For example:

   ;;;; Modified "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;  In this example, the module defines a table for storing greeting;;  names and two functions:;; ;;  - (say-hello-to "name");;  - (greet);;;;----------------------------------------------------------------------- (module helloWorld-mod GOVERNANCE  @doc "Update the hello-world project to store names."    (defcap GOVERNANCE () true)    (defschema hello-schema    @doc "Add a schema to store the 'name' variable for the greeting recipient."    name:string)   (deftable names:{hello-schema})   (defun say-hello-to (name)    @doc "Store 'name' to say hello with."    (write names "name" { 'name: name }))   (defun greet ()    @doc "Say hello using the stored 'name' from the hellos table."    (with-read names "name" { "name" := name }      (format "Hello, {}!" [name])))) (create-table names) (say-hello-to "world") ; store greeting recipient "world" in the names table(greet)                ; say hello!

   ;;;; Modified "Hello, world!" module;; ;;-----------------------------------------------------------------------;;;;  Use semicolons (;) for comments in smart contracts.;;  By convention, use:;;  ;;  - A single semicolon (;) for short notes on a single line of code. ;;  - Two semicolons (;;) to describe functions or other top-level forms.;;  - Three semicolons (;;;) to separate larger sections of code.;;;;  In this example, the module defines a table for storing greeting;;  names and two functions:;; ;;  - (say-hello-to "name");;  - (greet);;;;----------------------------------------------------------------------- (module helloWorld-mod GOVERNANCE  @doc "Update the hello-world project to store names."    (defcap GOVERNANCE () true)    (defschema hello-schema    @doc "Add a schema to store the 'name' variable for the greeting recipient."    name:string)   (deftable names:{hello-schema})   (defun say-hello-to (name)    @doc "Store 'name' to say hello with."    (write names "name" { 'name: name }))   (defun greet ()    @doc "Say hello using the stored 'name' from the hellos table."    (with-read names "name" { "name" := name }      (format "Hello, {}!" [name])))) (create-table names) (say-hello-to "world") ; store greeting recipient "world" in the names table(greet)                ; say hello!

3. Create a new file named 2-hello-world.repl file in your code editor.

4. Use the built-in (begin-tx) and (commit-tx) functions to define a transaction that executes the 2-hello-world.pact module:

   (begin-tx)  (load "2-hello-world.pact")(commit-tx)(begin-tx)  (helloWorld-mod.say-hello-to "Las Pistolas")  (helloWorld-mod.greet)(commit-tx)

   (begin-tx)  (load "2-hello-world.pact")(commit-tx)(begin-tx)  (helloWorld-mod.say-hello-to "Las Pistolas")  (helloWorld-mod.greet)(commit-tx)

5. Open a terminal shell and execute the 2-hello-world.repl file by running the following command:

   pact --trace 2-hello-world.repl

   pact --trace 2-hello-world.repl

   2-hello-world.repl:1:0:Trace: Begin Tx 02-hello-world.repl:2:0:Trace: Loading 2-hello-world.pact...2-hello-world.pact:15:0:Trace: Loaded module helloWorld-mod, hash ZcpdtgW86UIwvw_TjlgNreTErM2ECGEjh1m9nLu3AwA2-hello-world.pact:36:0:Trace: TableCreated2-hello-world.pact:38:0:Trace: Write succeeded2-hello-world.pact:39:0:Trace: Hello, world!2-hello-world.repl:3:0:Trace: Commit Tx 02-hello-world.repl:4:0:Trace: Begin Tx 12-hello-world.repl:5:0:Trace: Write succeeded2-hello-world.repl:6:0:Trace: Hello, Las Pistolas!2-hello-world.repl:7:0:Trace: Commit Tx 1Load successful

   2-hello-world.repl:1:0:Trace: Begin Tx 02-hello-world.repl:2:0:Trace: Loading 2-hello-world.pact...2-hello-world.pact:15:0:Trace: Loaded module helloWorld-mod, hash ZcpdtgW86UIwvw_TjlgNreTErM2ECGEjh1m9nLu3AwA2-hello-world.pact:36:0:Trace: TableCreated2-hello-world.pact:38:0:Trace: Write succeeded2-hello-world.pact:39:0:Trace: Hello, world!2-hello-world.repl:3:0:Trace: Commit Tx 02-hello-world.repl:4:0:Trace: Begin Tx 12-hello-world.repl:5:0:Trace: Write succeeded2-hello-world.repl:6:0:Trace: Hello, Las Pistolas!2-hello-world.repl:7:0:Trace: Commit Tx 1Load successful

Deploy the contract

1. Open the contract you want to deploy in your code editor.

   For example, open the 2-hello-world.pact file in your code editor.

2. Add the free namespace before the module definition in the file and update the module name to be unique.

   For example:

   (namespace "free")(module helloWorld-mod-pistolas GOVERNANCE  ...)

   (namespace "free")(module helloWorld-mod-pistolas GOVERNANCE  ...)

3. Save the changes in the code editor.

4. Open Chainweaver and select the testnet network.

5. Click Accounts in the Chainweaver navigation pane and verify that you have at least one account with funds on at least one chain in the test network.

   For example:

   

   If you don't have keys and at least one account on any chain on the test network,you need to generate keys, create an account, and fund the account on at least one chain before continuing.

6. Click Contracts in the Chainweaver navigation pane, then click Open File to select the contract you want to deploy.

7. Click Deploy to display the Configuration tab:

   • Select the Chain identifier for the chain where you want to deploy the contract.
   • Select a Transaction Sender.
   • Click Next.

8. On the Sign tab, select an Unrestricted Signing Key, then click Next.

9. On the Preview tab, scroll to see the Raw Response is "Hello, world!", then click Submit.

   After you click Submit, the transaction is sent to the blockchain. You can use the block explorer and the transaction request key to view the transaction results or wait for the transaction to be included in a block before closing the transaction submission dialog by clicking Done. When the transaction is mined into a block, you will have deployed your Hello World smart contract on the Kadena test network.

Call the deployed contract

1. Click Contracts in the Chainweaver navigation pane, if necessary, then click Module Explorer.

2. Under Deployed Contracts, search for your module name in the free namespace and chain where you deployed, then click Refresh to update the list of deployed contracts to display only your just-deployed contract.

   In this example, the unique module name is free.helloWorld-mod-pistolas and the contract was deployed on the testnet chain 1.

   

3. Click View to display the functions and capabilities defined in your contract.

4. Click Call to call the contract functions.

   • Click Call for the hello function to specify a new string in quotes, then click Next.
   • Click Next, select an Unrestricted Signing Key for this call, then click Next.
   • Click Submit to submit the transaction and commit the change.

   After the transaction is included in a block:

   • Click Call for the greet function, then click Next.

   • Select an Unrestricted Signing Key for this call, then click Next.

   • Scroll to see the Raw Response uses the string you specified for the hello function.

   • Click Submit if you want to submit the transaction to the blockchain or close the function call without submitting the transaction.