Final Project: Ship to Chain

Reading code is one thing. Shipping it is what makes you a NEAR developer. In this project you deploy your own contract to an account you control on testnet, call it, and submit it. Retr0 Academy then checks the chain and puts "Shipped: your-contract" on your public verify page.

What counts as shipped

The server accepts a contract when both of these are true on chain:

1. The contract account is your account or a sub-account of it (for example hello.you.testnet). Only you.testnet can create hello.you.testnet, so the name itself proves you made it.
2. The account has Wasm code deployed (its code_hash is not the empty hash 1111…).

If your contract also has a get_greeting view method, the verify page shows what it returns.

Step 1: create a sub-account for the contract

You need a testnet account first. If you don't have one, create it with the faucet (near create-account you.testnet --useFaucet). Then make a sub-account to hold the contract:

export YOU=you.testnet            # your account
export CONTRACT_ID=hello.$YOU     # the contract's account
near create-account "$CONTRACT_ID" --masterAccount "$YOU" --initialBalance 2 --networkId testnet

Keeping the contract on its own sub-account means you can redeploy or delete it without touching your main account.

Step 2: write the contract

Start from the official template and replace src/lib.rs with this. It stores a greeting, remembers the owner (whoever called new), and only lets the owner change it.

cargo near new hello-ship && cd hello-ship

use near_sdk::{env, log, near, AccountId, PanicOnDefault};
 
#[near(contract_state)]
#[derive(PanicOnDefault)]
pub struct Contract {
    greeting: String,
    owner: AccountId,
}
 
#[near]
impl Contract {
    #[init]
    pub fn new(greeting: String) -> Self {
        Self { greeting, owner: env::predecessor_account_id() }
    }
 
    // View call: free, anyone can read it.
    pub fn get_greeting(&self) -> String {
        self.greeting.clone()
    }
 
    // Change call: needs a signed transaction from the owner.
    pub fn set_greeting(&mut self, greeting: String) {
        assert_eq!(env::predecessor_account_id(), self.owner, "Only the owner can change the greeting");
        assert!(greeting.len() <= 140, "Keep it under 140 bytes");
        log!("greeting set to {}", greeting);
        self.greeting = greeting;
    }
}

The full version with unit tests is in the repo at contracts/hello-ship. Run cargo test to check the owner rule before you deploy.

Step 3: build and deploy

cargo near build non-reproducible-wasm
near deploy "$CONTRACT_ID" ./target/near/hello_ship.wasm \
  --initFunction new --initArgs '{"greeting":"gm from a Retr0 Academy student"}' \
  --networkId testnet

--initFunction runs new in the same transaction as the deploy, so nobody can initialize your contract before you do.

Step 4: call it

near view "$CONTRACT_ID" get_greeting '{}' --networkId testnet
near call "$CONTRACT_ID" set_greeting '{"greeting":"shipped!"}' --accountId "$YOU" --networkId testnet

The first is a free view call. The second is a change call: your key signs it, you pay a tiny bit of gas, and the contract checks that you are the owner.

Step 5: check your deploy from the browser

This page reads your contract with plain JSON-RPC, the same way the verify page does. Put in your contract id and press Check. Open it in the Playground to change it.

<main>
<h1>Is my contract live?</h1>
<div class="row">
  <input id="id" value="demo-learner.retr0school.testnet" spellcheck="false" aria-label="Contract account id" />
  <button type="button" id="go">Check</button>
</div>
<pre id="out">Press Check.</pre>
</main>

Step 6: submit it

Enter your account and the contract account. The server reads the chain (no signature, no gas), checks the two rules above, and links the contract to your verify page.

How the link is stored

The certificate contract is not changed, so existing certificates stay exactly as minted. The server keeps a small record signed with its key (ships/<you>.json), and the verify page re-checks your contract's code_hash on chain every time someone opens it. If you redeploy, it shows "redeployed since check"; submit again to refresh it.