A Beautiful Dance: Synchronous Channels in Go

waltz.go

// what a beautiful application of synchronous channels!

// source: https://blog.mozilla.org/services/2014/03/12/sane-concurrency-with-go/

type Account struct {
  balance float64
  deltaChan chan float64
  balanceChan chan float64
  errChan chan error
}

func NewAccount() (a *Account) {
  a = &Account{
    balance:     balance,
    deltaChan:   make(chan float64),
    balanceChan: make(chan float64),
    errChan:     make(chan error),
  }
  go a.run()
}

func (a *Account) Balance() float64 {
  return <-a.balanceChan
}

func (a *Account) Deposit(amount float64) error {
  a.deltaChan <- amount
  return <-a.errChan
}

func (a *Account) Withdraw(amount float64) error {
  a.deltaChan <- -amount
  return <-a.errChan
}

func (a *Account) applyDelta(amount float64) error {
  newBalance := a.balance + amount
  if newBalance < 0 {
    return errors.New("Insufficient funds")
  }
  a.balance = newBalance
  return nil
}

func (a *Account) run() {
  var delta float64
  for {
    select {
      case delta = <-a.deltaChan:
      a.errChan <- a.applyDelta(delta)
      case a.balanceChan <- a.balance:
      // Do nothing, we've accomplished our goal w/ the channel put.
    }
  }
}

beautiful.

<3