latest

Returns the latest revision of an on chain object. Note that the latest revision of an object can be either unspent or spent.

Type

  latest(rev: string): Promise<string>

Parameters

`rev`

A revision encoded as a string of the form <transaction-id>:<output-number>.

Return Value

Returns the latest revision of the same on chain object - that is, its id.

Description

If latest is called with a revision for which no output exists, it throws an error Rev not found. If the output exists but contains no object, the same error is thrown. If the output contains an object, latest will return the latest revision of an object as indicated by the arrows in the figure below.

Example

import { Computer, Contract } from '@bitcoin-computer/lib'
import { chain, expect, network, url } from '../../utils/index.js'

describe('latest', () => {
  // A smart contract
  class Counter extends Contract {
    n: number

    constructor() {
      super({ n: 0 })
    }

    inc() {
      this.n += 1
    }
  }

  let computer: Computer

  before('Create and fund wallet', async () => {
    computer = new Computer({ chain, network, url })
    await computer.faucet(1e8)
  })

  it('Should work if an object is not updated', async () => {
    const counter = await computer.new(Counter, [])

    expect(await computer.latest(counter._id)).eq(counter._id)
  })

  it('Should work if an object is updated', async () => {
    const counter = await computer.new(Counter, [])
    await counter.inc()

    expect(await computer.latest(counter._id)).eq(counter._rev)
    expect(await computer.latest(counter._rev)).eq(counter._rev)
  })

  it('Should throw an error with a revision that does not exist', async () => {
    const noOutput = '0'.repeat(64) + ':0'

    // Throws because there is no output with that revision
    await expect(computer.latest(noOutput)).to.be.rejectedWith(/Rev .* not found/)
  })

  it('Should throw an error with a revision that does not contain an object', async () => {
    const counter = await computer.new(Counter, [])
    const noObject = counter._id.split(':')[0] + ':1'

    // Throws because there is no object at the output with that revision
    await expect(computer.latest(noObject)).to.be.rejectedWith(/Rev .* not found/)
  })
})

Source