ReactiveCocoa 4 - Need help on validate input upon button tap - ios

Question

I'm new to ReactiveCocoa, and I'm trying to figure out the syntax for validating form input upon button tap. There are quite a number of sample code for validTextSignal, but most of them either hooked into Action-enableIf, or handle UI bindings directly.
The idea is simple, I have a login screen, with email and password input. What I want is to handle validation upon Login tap to show an UIAlertView (eg. "Please input your email").
Here's what I figured out after awhile, the code works, but I'm not certain whether this should be the way to do it.
self.s_formErrorMessage <~ combineLatest(s_email.producer, s_password.producer)
.map({ (email, password) in
if adminNumber.isEmpty {
return "Please input admin number"
} else if password.isEmpty {
return "Please input password"
}
return ""
})
And here's how I use it, just simply use the value in button TouchUpInside
btn_login.rac_signalForControlEvents(.TouchUpInside).subscribeNextAs { (button: UIButton) in
if !self.viewModel.s_formErrorMessage.value.isEmpty {
self.showAlert("", message: self.viewModel.s_formErrorMessage.value)
}
}
Also, is there anyway we can capture Interrupted event from Action-enableIf false?
Any suggestion for better approach would be much appreaciated.
Cheers

Answer 1

Action use with button for disabled while do request (for example login request). So in this case need disabled button if not valid input.
Or binding error text in prompt text field if not valid.
But if you want just show alert with text error about failed valid fields you cat try this code:
btn_login.rac_signalForControlEvents(.TouchUpInside)
.toSignalProducer().map { [unowned self] _ in
return self.viewModel.s_formErrorMessage.value
}.filter { !$0.isEmpty }
.startWithNext { [unowned self] text in
self.showAlert("", message: text)
}