The Deployable Trait

Tact doesn't support classical class inheritance, but contracts can implement traits.

One commonly used trait is Deployable, which implements a simple receiver for the Deploy message. This helps deploy contracts in a standardized manner.

All contracts are deployed by sending them a message. While any message can be used for this purpose, best practice is to use the special Deploy message.

This message has a single field, queryId, provided by the deployer (usually set to zero). If the deployment succeeds, the contract will reply with a DeployOk message and echo the same queryId in the response.

If you're using Tact's auto-generated TypeScript classes to deploy, sending the deploy message should look like:

const msg = { $$type: "Deploy", queryId: 0n };
await contract.send(sender, { value: toNano(1) }, msg);

You can see the implementation of the trait here. Notice that the file deploy.tact needs to be imported from the standard library using the import keyword.

All Examples

import "@stdlib/deploy";

contract Addresses with Deployable {

    // contract persistent state variables
    // we have three representations of the same address
    a1: Address = address("EQCD39VS5jcptHL8vMjEXrzGaRcCVYto7HUn4bpAOg8xqB2N"); // bouncable (same foundation wallet)
    a2: Address = address("UQCD39VS5jcptHL8vMjEXrzGaRcCVYto7HUn4bpAOg8xqEBI"); // non-bounceable (same foundation wallet)
    a3: Address;

    a4: Address;
    a5: Address;
    a6: Address;

    init() {
        // this is the third representation of the same address
        self.a3 = newAddress(0, 0x83dfd552e63729b472fcbcc8c45ebcc6691702558b68ec7527e1ba403a0f31a8); // raw (same foundation wallet)
        
        // here are a few other important addresses
        self.a4 = newAddress(0, 0); // the zero address (nobody)
        self.a5 = myAddress();      // address of this contract
        self.a6 = sender();         // address of the deployer (the sender during init())
    }

    receive("show all") {
        /// addresses cannot currently be dumped
        /// TODO: https://github.com/tact-lang/tact/issues/16
        /// dump(self.a1);
    }

    receive("show ops") {
        // temporary variable
        let a: Address = address("EQCD39VS5jcptHL8vMjEXrzGaRcCVYto7HUn4bpAOg8xqB2N"); // bouncable (same foundation wallet)

        dump(a == self.a1);
        dump(a == self.a2);
        dump(a == self.a3);
        
        dump(a == self.a4);
        dump(a != self.a5);
    }

    get fun result(): Address {
        return self.a1;
    }
}