TZIP-16 Contract Metadata and Views

The @taquito/tzip16 package allows retrieving metadata associated with a smart contract. These metadata can be stored on-chain (tezos-storage) or off-chain (HTTP(S) or IPFS). The package also provides a way to execute the MichelsonStorageView found in the metadata. More information about the TZIP-16 standard can be found here.

How to use the tzip16 package

The package can be used as an extension to the well known Taquito contract abstraction.

1. We first need to create an instance of Tzip16Module and add it as an extension to our TezosToolkit

Using the default Metadata Provider

The constructor of the Tzip16Module takes an optional MetadataProvider as a parameter. When none is passed, the default MetadataProvider of Taquito is instantiated and the default handlers (HttpHandler, IpfsHandler, and TezosStorageHandler) are used.

import { TezosToolkit } from '@taquito/taquito';
import { Tzip16Module } from '@taquito/tzip16';

const Tezos = new TezosToolkit('rpcUrl');
Tezos.addExtension(new Tzip16Module());

Using a custom Metadata Provider

In some cases, we may want to use a customized metadata provider. The constructor of the Tzip16Module class takes an optional metadata provider as a parameter. This allows to inject a custom metadata provider with custom protocol handlers if desired. For example, if we want to use a different IPFS gateway than the default one, which is ipfs.io, or if we want to use a different HTTP handler to support authentication or custom headers. Here is an example:

import { Handler, IpfsHttpHandler, TezosStorageHandler, MetadataProvider } from '@taquito/tzip16';

const Tezos = new TezosToolkit('rpcUrl');

// The constructor of the `MetadataProvider` class takes a `Map<string, Handler>` as a parameter.
const customHandler = new Map<string, Handler>([
  ['ipfs', new IpfsHttpHandler('gateway.ipfs.io')], // Constructor of IpfsHttpHandler takes an optional gateway
  ['http', 'customHttpHandler'], // Custom HTTP(S) handler
  ['https', 'customHttpHandler'],
  ['tezos-storage', new TezosStorageHandler()],
]);

const customMetadataProvider = new MetadataProvider(customHandler);
Tezos.addExtension(new Tzip16Module(customMetadataProvider));

A list of public gateways is accessible here.

2. Use the tzip16 function to extend a contract abstraction

const contract = await Tezos.contract.at("contractAddress", tzip16)

3. Call the methods of the Tzip16ContractAbstraction class

The namespace tzip16() need to be specified when calling a method of the Tzip16ContractAbstraction class:

const metadata = await contract.tzip16().getMetadata();
const views = await contract.tzip16().metadataViews();

All other methods of the ContractAbstraction class can be called as usual on the contract object.

Get the metadata

The getMetadata method returns an object which contains the URI, the metadata in JSON format, an optional SHA256 hash of the metadata and an optional integrity check result.

A sequence diagram can be found here.

Tezos-storage example

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16 } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT1Sw8tCxQLQQGBw8VNFjoJpESxRXjC5XEii"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { println(`Fetching the metadata for ${contractAddress}...`); return contract.tzip16().getMetadata(); }) .then (metadata => { println(JSON.stringify(metadata, null, 2)); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16 } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT1Sw8tCxQLQQGBw8VNFjoJpESxRXjC5XEii";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  println(`Fetching the metadata for ${contractAddress}...`);
  return contract.tzip16().getMetadata();
})
.then (metadata => {
  println(JSON.stringify(metadata, null, 2));
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

HTTPS examples

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16 } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT1P8w7Xeobq4xSk4W2JTjfDgQHxkTeg9ftT"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { println(`Fetching the metadata for ${contractAddress}...`); return contract.tzip16().getMetadata(); }) .then (metadata => { println(JSON.stringify(metadata, null, 2)); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16 } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT1P8w7Xeobq4xSk4W2JTjfDgQHxkTeg9ftT";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  println(`Fetching the metadata for ${contractAddress}...`);
  return contract.tzip16().getMetadata();
})
.then (metadata => {
  println(JSON.stringify(metadata, null, 2));
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

An example having a SHA256 hash:

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16 } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT1KB3L4p27PsDs27n2E7ZY9fxVXewHDEbVP"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { println(`Fetching the metadata for ${contractAddress}...`); return contract.tzip16().getMetadata(); }) .then (metadata => { println(JSON.stringify(metadata, null, 2)); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16 } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT1KB3L4p27PsDs27n2E7ZY9fxVXewHDEbVP";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  println(`Fetching the metadata for ${contractAddress}...`);
  return contract.tzip16().getMetadata();
})
.then (metadata => {
  println(JSON.stringify(metadata, null, 2));
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

IPFS example

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16 } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT1NP2ZVLxWaSBQryDzUujmdv27ubJWZRckv"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { println(`Fetching the metadata for ${contractAddress}...`); return contract.tzip16().getMetadata(); }) .then (metadata => { println(JSON.stringify(metadata, null, 2)); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16 } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT1NP2ZVLxWaSBQryDzUujmdv27ubJWZRckv";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  println(`Fetching the metadata for ${contractAddress}...`);
  return contract.tzip16().getMetadata();
})
.then (metadata => {
  println(JSON.stringify(metadata, null, 2));
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

Execute off-chain views

A sequence diagram can be found here.

In the next example, we will run a view named someJson that can be found in the metadata of the contract KT1Vms3NQK8rCQJ6JkimLFtAC9NhpAq9vLqE. When we inspect those metadata, we can see that this view takes no parameter, has a returnType of bytes and has the following code:

"code": 
[
  {
    "prim": "DROP",
    "args": [],
    "annots": []
  },
  {
    "prim": "PUSH",
    "args": [
      {
        "prim": "bytes",
        "args": [],
        "annots": []
      },
      {
        "bytes": "7b2268656c6c6f223a22776f726c64222c226d6f7265223a7b226c6f72656d223a34322c22697073756d223a5b22222c226f6e65222c2232225d7d7d"
      }
    ],
    "annots": []
  }
]

Try to run the view:

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16, bytes2Char } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT1Vms3NQK8rCQJ6JkimLFtAC9NhpAq9vLqE"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { println(`Initialising the views for ${contractAddress}...`); return contract.tzip16().metadataViews(); }) .then (views => { println(`The following view names were found in the metadata: ${Object.keys(views)}`); return views.someJson().executeView() }).then (result => { println(`Result of the view someJson: ${result}`); println(`Transform result to char: ${bytes2Char(result)}`); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16, bytes2Char } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT1Vms3NQK8rCQJ6JkimLFtAC9NhpAq9vLqE";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  println(`Initialising the views for ${contractAddress}...`);
  return contract.tzip16().metadataViews();
})
.then (views => {
  println(`The following view names were found in the metadata: ${Object.keys(views)}`);
  return views.someJson().executeView()
}).then (result => {
  println(`Result of the view someJson: ${result}`);
  println(`Transform result to char: ${bytes2Char(result)}`);
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

In the next example, we will run a view named multiply-the-nat-in-storage that can be found in the metadata of the contract KT19rDkTYg1355Wp1XM5Q23CxuLgRnA3SiGq. When we inspect those metadata, we can see that this view takes a nat has a parameter, has a returnType of nat and has the following instructions: DUP, CDR, CAR, SWAP, CAR, MUL.

Try to run the view:

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { Tzip16Module, tzip16 } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); Tezos.addExtension(new Tzip16Module()); const contractAddress = "KT19rDkTYg1355Wp1XM5Q23CxuLgRnA3SiGq"; Tezos.contract.at(contractAddress, tzip16) .then(contract => { return contract.storage() .then(storage => { println(`The nat in the storage of the contract is: ${storage[0]}`); println(`Initialising the views for ${contractAddress}...`); return contract.tzip16().metadataViews(); })}) .then (views => { println(`The following view names were found in the metadata: ${Object.keys(views)}`); return views['multiply-the-nat-in-storage']().executeView(10) }).then (result => { println(`Result of the view 'multiply-the-nat-in-storage': ${result}`); }) .catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { Tzip16Module, tzip16 } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

Tezos.addExtension(new Tzip16Module());

const contractAddress = "KT19rDkTYg1355Wp1XM5Q23CxuLgRnA3SiGq";

Tezos.contract.at(contractAddress, tzip16)
.then(contract => {
  return contract.storage()
.then(storage => {
  println(`The nat in the storage of the contract is: ${storage[0]}`);
  println(`Initialising the views for ${contractAddress}...`);
  return contract.tzip16().metadataViews();
})})
.then (views => {
  println(`The following view names were found in the metadata: ${Object.keys(views)}`);
  return views['multiply-the-nat-in-storage']().executeView(10)
}).then (result => {
  println(`Result of the view 'multiply-the-nat-in-storage': ${result}`);
})
.catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result

Execute a custom view

In the next example we execute the view multiply-the-nat-in-storage in a custom way:

Live Editor

// import { TezosToolkit } from '@taquito/taquito'; // import { MichelsonStorageView } from "@taquito/tzip16"; // const Tezos = new TezosToolkit('rpc_url'); const contractAddress = "KT19rDkTYg1355Wp1XM5Q23CxuLgRnA3SiGq"; Tezos.contract.at(contractAddress) .then(contract => { const view = new MichelsonStorageView( 'test', // view name contract, // contract abstraction Tezos.rpc, // rpc { "prim": "nat" }, // returnType [{ "prim": "DUP" },{ "prim": "CDR" },{ "prim": "CAR" },{ "prim": "SWAP" },{ "prim": "CAR" }, { "prim": "MUL" }], // code of the view { "prim": "nat" } // parameter type ) view.executeView(2) .then(result => { println(`Result of the custom view: ${result}`) })}).catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

// import { TezosToolkit } from '@taquito/taquito';
// import { MichelsonStorageView } from "@taquito/tzip16";
// const Tezos = new TezosToolkit('rpc_url');

const contractAddress = "KT19rDkTYg1355Wp1XM5Q23CxuLgRnA3SiGq";

Tezos.contract.at(contractAddress)
.then(contract => {
  const view = new MichelsonStorageView(
    'test', // view name
    contract, // contract abstraction
    Tezos.rpc, // rpc
    { "prim": "nat" }, // returnType
    [{ "prim": "DUP" },{ "prim": "CDR" },{ "prim": "CAR" },{ "prim": "SWAP" },{ "prim": "CAR" }, { "prim": "MUL" }], // code of the view
    { "prim": "nat" } // parameter type
  )
              
view.executeView(2)
.then(result => {
  println(`Result of the custom view: ${result}`)
})}).catch(error => println(`Error: ${JSON.stringify(error, null, 2)}`));

Result