B/O - Chain of Responsibility

• Category: behavioral
• Type: object
• Motivation: build a chain of object, request from one end and keeps going from object to object till it finds the suitable handler

do {
  var bank = Bank(balance: 100)
  var paypal = Paypal(balance: 200)
  bank.setNext(paypal)

  bank.pay(amount: 30)
}

protocol Account
{
    var balance: Float {set get}
    var sucessor: Account? {set get}
}

extension Account
{
    mutating func pay(amount: Float)
    {
        if canPay(amount) {
            balance -= amount
            print("\(String(describing: type(of: self))) paid, balance: \(balance)")
        } else if var account = sucessor {
            account.pay(amount: amount)
        } else {
            print("none accounts have enought balance")
        }
    }

    func canPay(_ amount: Float) -> Bool
    {
        amount <= balance
    }

    mutating func setNext(_ account: Account)
    {
        sucessor = account
    }
}

struct Bank: Account
{
    var balance: Float
    var sucessor: Account?
}

struct Paypal: Account
{
    var balance: Float
    var sucessor: Account?
}