Tzip16
@taquito/tzip16 is an npm package that provides developers with TZIP-016 functionality for Taquito. TZIP-016 is a standard for encoding access to smart contract metadata either on-chain or off-chain. The @taquito/tzip16 package allows developers to retrieve the metadata associated with a smart contract and execute the off-chain views found in the metadata.
Contract metadata gathers valuable information about the contract that is not directly used for its operation. According to TZIP-016, a contract with metadata must include in its storage a big_map named %metadata of the following type: (big_map %metadata string bytes). The big_map must have an empty string as a key where its value is a byte-encoded URI representing the metadata location. Contract metadata can be located on-chain or off-chain (web services or IPFS). Please refer to the following link for complete documentation on TZIP-016.
When using the @taquito/tzip16 package, developers can retrieve metadata of a contract based on its address. The underlying steps performed by Taquito are to find the URI in the contract storage, decode it, extract the metadata depending on the protocol (tezos-storage, HTTP(S) or IPFS), perform an integrity check if the URI contains a sha256 hash, and return the metadata to the user.
Another functionality of the @taquito/tzip16 package allows executing off-chain views. If a contract contains views in its metadata, Taquito builds an ordinary JavaScript object with methods corresponding to the views name.
The package can be used to extend the well-known Taquito contract abstraction. The @taquito/tzip16 and the @taquito/taquito packages need to be installed as follows:
``
npm i --save @taquito/tzip16
npm i --save @taquito/taquito
Create an instance of the Tzip16Module and add it as an extension to the TezosToolkit
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. MetadataProvider
The can be customized by the user if needed.
Use the tzip16 function to extend a contract abstraction
`js
import { TezosToolkit } from '@taquito/taquito';
import { Tzip16Module } from '@taquito/tzip16';
import { tzip16 } from '@taquito/tzip16';
const Tezos = new TezosToolkit('https://YOUR_PREFERRED_RPC_URL');
Tezos.addExtension(new Tzip16Module());
const contract = await Tezos.contract.at("contractAddress", tzip16)
`
`ts`
const metadata = await contract.tzip16().getMetadata();
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.
`ts``
// Initialize off-chain views
const metadataViews = await contractAbstraction.tzip16().metadataViews();
const viewResult = await metadataViews.nameOfTheView().executeView(paramOfTheView);
See the top-level https://github.com/ecadlabs/taquito file for details on reporting issues, contributing, and versioning.
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