# Transaction

The Transaction class exported from @bitcoin-computer/lib extends the Transaction class exported from @bitcoin-computer/nakamotojs and therefore has all of its properties and methods (see here).

In addition it has methods and properties related to the Bitcoin Computer protocol, as well as convenience methods for developing Bitcoin-based applications.

# Properties

# inRevs

Returns the revisions of on-chain objects spent by the transaction.

# outRevs

Returns the revisions of on-chain objects created by the transaction.

# Methods

# fromTxId

Returns a Transaction object from a transaction id.

# onChainMetaData

Returns a Transaction object from a transaction buffer.

# Example

class A extends Contract {
  n: number
  constructor() {
    super({ n: 1 })
  }

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

// Create and fund client side wallet
const computer = new Computer()
await computer.faucet(1e8)
const { wallet } = computer
const { restClient } = wallet

// Create on-chain object and retrieve its transaction
const a = await computer.new(A)
const txId1 = a._id.slice(0, 64)
const tx1 = await Transaction.fromTxId({ txId: txId1, restClient })

// tx1's inRevs and outRevs reflect the objects creation
expect(tx1.inRevs).deep.eq([])
expect(tx1.outRevs).deep.eq([a._id])

// tx1's metaData contains the constructor call
expect(tx1.onChainMetaData).deep.eq({
  exp: `${A} new A()`,
  env: {},
  mod: '',
  v: Computer.getVersion(),
  ioMap: [],
})

// Update on-chain object and retrieve its transaction
await a.inc()
const txId2 = a._rev.slice(0, 64)
const tx2 = await Transaction.fromTxId({ txId: txId2, restClient })

// tx2's inRevs and outRevs reflect the objects update
expect(tx2.inRevs).deep.eq([a._id])
expect(tx2.outRevs).deep.eq([a._rev])

// tx2's metaData contains the function call
expect(tx2.onChainMetaData).deep.eq({
  exp: `__bc__.inc()`,
  env: { __bc__: 0 },
  mod: '',
  v: Computer.getVersion(),
  ioMap: [0],
})