ReactiveCocoa_ValidatingPropertyExample.swift

enum PasswordError: Error {
    case tooShort
    case tooLong
    case noCapitalLetter
}

let password = MutableProperty("")
let validated: ValidatingProperty<String, PasswordError> = ValidatingProperty(password, {
    if $0.count < 5 {
        return .invalid(.tooShort)
    }
    if $0.count > 10 {
        return .invalid(.tooLong)
    }
    if $0.filter({ character in String(character).uppercased() == String(character) }).first != .none {
        return .valid
    }
    return .coerced($0.capitalized, .noCapitalLetter)
})

validated.producer.startWithValues {
    print("Producer Value -", $0)
    print("Value - ", validated.value)
}
validated.result.producer.startWithValues {
    print("Result -", $0)
}
password.value = "hi"
password.value = "HELLO"
password.value = "too loooooong"
password.value = "hello"