Working with Enums ( Add functions using Protocol )

Enum.swift

// A Protocol that has update function to update Device State
protocol State {
    
   // function is mutating so that Enum and structure can update the self
   mutating func update()
}

// Enum wit Active and Inactive Device state
enum DeviceState : State {
    
    case Active, Inactive
    
    // Implement the update method to change device state
    mutating func update() {
        
        // check current device state and update
        if self == .Inactive {
            self = .Active
        } else {
            self = .Inactive
        }
    }
}

// creating object with Active state
var deviceState = DeviceState.Active
print(deviceState) // Output : Active

// call method on enum object to update state
deviceState.update()

print(deviceState) // Output : Inactive