Overview

In this tutorial we will retrieve the data contract created in the Register a Data Contract tutorial.

Prerequisites

node.js (v12+)
Basic familiarity with JavaScript asychronous functions using async/await
The Dash JavaScript SDK is initialized (covered in Connecting to a Network)

Code

Retrieving a data contract

const Dash = require('dash');

const client = new Dash.Client();

const retrieveContract = async () => {
  const contractId = '3iaEhdyAVbmSjd59CT6SCrqPjfAfMdPTc8ksydgqSaWE';
  return client.platform.contracts.get(contractId);
};

retrieveContract()
  .then((d) => console.dir(d.toJSON(), { depth: 5 }))
  .catch((e) => console.error('Something went wrong:\n', e))
  .finally(() => client.disconnect());

Updating the client app list

📘
In many cases it may be desirable to work with a newly retrieved data contract using the <contract name>.<contract document> syntax (e.g. dpns.domain). Data contracts that were created after the client was initialized or not included in the initial client options can be added via client.getApps().set(...).

const Identifier = require('@dashevo/dpp/lib/Identifier');
const myContractId = 'a contract ID';
const myContract = client.platform.contracts.get(myContractId);

client.getApps().set('myNewContract', {
  contractId: Identifier.from(myContractId),
  contract: myContract,
});

Example Data Contract

The following example response shows a retrieved contract:

{
   "protocolVersion":0,
   "$id":"C96rCVpck4RdBQXG3zzP5KH4RKzfKVTsmTauu8FQenJi",
   "$schema":"https://schema.dash.org/dpp-0-4-0/meta/data-contract",
   "ownerId":"FgPx8YHbWv4rMeiP52DfmnAXGtjiCiSaNKCbgT7eCRxh",
   "documents":{
      "note":{
         "properties":{
            "message":{
               "type":"string"
            }
         },
         "additionalProperties":false
      }
   }
}

📘
Please refer to the data contract reference page for more comprehensive details related to contracts and documents.

What's Happening

After we initialize the Client, we request a contract. The platform.contracts.get method takes a single argument: a contract ID. After the contract is retrieved, it is displayed on the console.

The second code example shows how the contract could be assigned a name to make it easily accessible without initializing an additional client.