Hands-On Design Patterns with Swift

Using enums

First, let's see how this reader could look if we implement its state with an enum:

class CardReader {

Implement the state with the enum, with all the possible state values, as follows:

enum State {    case unknown    case waiting    case reading    case read(CardInfo)    case failed(Error)}

Use the private var state property so that no one can mutate the state from outside:

private var state: State = .unknown

The main routine is implemented as follows. For each loop, it will print the current state:

    func start() {        while true {            print("\(state)")            switch state {            case .unknown:                state = .waiting            case .waiting:

When we're waiting, we wait for a card to be detected by the radio. When the card is detected, we change the state to reading:

 if seenCard() ...