Value Objects

Extend vo(name, schema) to get a validated value with domain methods.

Import

import { integer, vo } from '@marcelsud/accord'

Usage

class Balance extends vo('Balance', integer) {
  inc(amount: number): Balance {
    return Balance.of(this.value + amount)
  }
}

const balance = Balance.of(100).inc(50)
balance.snapshot() // 150
balance.snapshot((cents) => ({ cents })) // { cents: 150 }

API

Class.of(value)

Validates value against the schema and returns an instance of your subclass. Invalid values throw a TypeError.

this.value

The validated raw value (protected). It's a structuredClone copy of what you passed in.

snapshot()

Returns a copy of the raw value.

snapshot(project)

Copies the raw value and maps it with project.

Class.valueObjectName

The name you passed to vo().

Value objects and state

Keep aggregate state plain. Use value objects for the arithmetic, then write raw values back:

deposit(amount: number) {
  const balance = Balance.of(state.balance).inc(amount).snapshot()
  state.balance = balance
  // ...
}

TIP

Use raw values that round-trip through structuredClone. That's what Accord stores.