How to provide the custom message for validation

[azamsharp]

How can I provide a custom message for validation like:

Validated(.nonEmpty("Username cannot be empty"))
var username: String?

Where can I provide "Username cannot be empty" message?

[SvenTiigi]

Hey @azamsharp,

Sorry for the delayed response.

Currently the default .nonEmpty validation is defined as an extension on the Validation where the Value conforms to the Collection protocol and doesn't accept any custom messages instead it defines its own:

public extension Validation where Value: Collection {
    
    /// The non empty Validation
    static var nonEmpty: Validation {
        return .init { value in
            if !value.isEmpty {
                return .success
            } else {
                return .failure("Is empty")
            }
        }
    }

}

Of course this could be refactored into a function which should fit your needs.

public extension Validation where Value: Collection {
    
    static func nonEmpty(failureMessage: String = "Is Empty") -> Validation {
        return .init { value in
            if !value.isEmpty {
                return .success
            } else {
                return .failure(.init(message: failureMessage))
            }
        }
    }

}

As ValidatedPropertyKit hasn't got an offical 1.0 release version there is definitely a lot that should be improved especially the error handling.

Please feel free to open up a PR to get things started ✌️

[Thongvor]

How can I override/extend "isEmail" or any other regEx Validation to show a custom error message?

[SvenTiigi]

Hey @Thongvor,

unfortunately I could not find the time yet to improve the Error handling mechanism so that you can provide your own Error enum or string. Thats the reason why ValidatedPropertyKit has no official 1.0 version.

As of for now you can switch on the validatedValue from the projected value of the PropertyWrapper which is a Result type:

@Validated(.isEmail)
var email: String?

...

switch _email.validatedValue {
case .success(let value):
    break
case .failure(let validationError):
    // Use the ValidationError or use any other error message
    break
}

[Thongvor]

@SvenTiigi, thank you for your answer!
I found a working solution without using switch on the validatedValue,
if someone needs it:

public extension Validation where Value == String {
    static func isEmail(errorMessage: String = "Invalid email format") -> Validation {
        return .init {
            return Validation.isEmail.isValid(value: $0).flatMapError {_ in
                return .failure(.init(message: errorMessage))}
        }
    }
}

[mikekllr]

The fix doesn't seem to work anymore. However, I found a very cumbersome alternative by setting an event in the text fields and querying the .isValid attribute. I really like the repo and it integrates seamlessly with swiftui. Is there a way to adapt the repo to be able to output error messages?