Swift :: Validator input

1.swift

enum ValidateResult {
    case valid
    case invalid(error: Error)
}

2.swift

enum UsernameValidateError: Error {
    case empty
    case tooShort
    case tooLong
}

3.swift

protocol Validator {
    func validate(value: String) -> ValidateResult
}

4.swift

struct EmptyValidator: Validator {
    
    private let invalidError: Error
    
    init(invalidError: Error) {
        self.invalidError = invalidError
    }
    
    func validate(value: String) -> ValidateResult {
        if value.isEmpty {
            return .invalid(error: invalidError)
        }
        return .valid
    }
    
}

5.swift

struct UsernameTooShortValidator: Validator {
    
    func validate(value: String) -> ValidateResult {
        if value.characters.count < 5 {
            return .invalid(error: UsernameValidateError.tooShort)
        }
        return .valid
    }
    
}

6.swift

struct UsernameTooLongValidator: Validator {
    
    func validate(value: String) -> ValidateResult {
        if value.characters.count > 20 {
            return .invalid(error: UsernameValidateError.tooLong)
        }
        return .valid
    }
    
}

7.swift

struct Validators: Validator {
    
    private let validators: [Validator]
    
    init(validators: Validator...) {
        self.validators = validators
    }
    
    func validate(value: String) -> ValidateResult {
        for validator in validators {
            switch validator.validate(value: value) {
            case .valid:
                break
            case .invalid(let error):
                return .invalid(error: error)
            }
        }
        return .valid
    }
}

8.swift

let usernameValidator: Validator
    = Validators(validators:
        EmptyValidator(invalidError: UsernameValidateError.empty),
        UsernameTooShortValidator(),
        UsernameTooLongValidator()
)

print(usernameValidator.validate(value: ""))
print(usernameValidator.validate(value: "123"))
print(usernameValidator.validate(value: "123451234512345123451"))
print(usernameValidator.validate(value: "123456"))