error

error.swift

enum PhoneError: Error { case unknown case batteryLow(batteryLevel: Int) }
throw PhoneError.batteryLow(batteryLevel: 20)

- 던져진 오류를 처리하기 위한 작업이 필요하다
```swift
func checkPhoneBatteryStatus(batteryLevel: Int) throws -> String {
    guard batteryLevel != -1 else { throw PhoneError.unknown }
    guard batteryLevel > 20 else { throw PhoneError.batteryLow(batteryLevel: batteryLevel) }
    return "배터리 상태 정상"
}

// do - catch example
do {
    try checkPhoneBatteryStatus(batteryLevel: -1)
} catch PhoneError.unknown {
    print("Unknown")
} catch PhoneError.batteryLow(let batteryLevel) {
    print("Battery power shortage: \(batteryLevel)%")
} catch {
    print("Etc error: \(error)")
}

// try? / try! -> 동작하던 코드가 에러를 던지면 return 값 nil / try!는 에러를 던지지않는다고 확실할 때 사용 (근데 왜 try 씀?)
let status = try? checkPhoneBatteryStatus(batteryLevel: -1)
let status = try! checkPhoneBatteryStatus(batteryLevel: -1)

https://github.com/HackPeel/hackpeel-22

https://github.com/HackPeel/hackpeel-24