Prerequisites

• General prerequisites (Node.js / Hellar SDK installed)
• A wallet mnemonic with some funds in it: Tutorial: Create and Fund a Wallet
• A Hellar Platform Identity: Tutorial: Register an Identity

Code

Defining contract documents

As described in the data contract explanation, data contracts must include one or more developer-defined documents.

The most basic example below (tab 1) demonstrates a data contract containing a single document type (note) which has a single string property (message).

The second tab shows the same data contract with an index defined on the $ownerId field. This would allow querying for documents owned by a specific identity using a where clause.

The third tab shows a data contract requiring the optional $createdAt and $updatedAt base fields. Using these fields enables retrieving timestamps that indicate when a document was created or modified.

The fourth tab shows a data contract using a byte array. This allows a contract to store binary data.

The fifth tab shows a data contract configured to store contract history. This allows all contract revisions to be retrieved in the future as needed.

🚧

Since Platform v0.1.0, each document property must assign position value to support backwards compatibility for contract updates.

Since Platform v0.1.0, an index can only use the ascending order (asc). Future updates will remove this restriction.

JSON

// 1. Minimal contract { "note": { "type": "object", "properties": { "message": { "type": "string", "position": 0 } }, "additionalProperties": false } }

JSON

`// 2. Indexed { "note": { "type": "object", "indices": [ { "name": "ownerId", "properties": [{ "$ownerId": "asc" }], "unique": false } ], "properties": { "message": { "type": "string", "position": 0 } }, "additionalProperties": false } }

/* An identity's documents are accessible via a query including a where clause like: { where: [['$ownerId', '==', 'an identity id']], } */`

JSON