Combining RAC signals and updating UI

Question

I'm using Swift 2.1 and ReactiveCocoa 4.0.4 alpha 1. I'm combining multiple signals to enable a button based on if they have valid inputs. The following code works correctly, but I'm wondering if there is a more elegant and efficient way of accomplishing this with the ReactiveCocoa APIs, as well as if this is the proper way to be using the API in Swift.

 let sig0 = firstTextField.rac_textSignal()
 .max(self.firstTextField, max: maxLength)
 .map{ next in
 if let str = next as? String {
 return str.characters.count > 0
 } else {
 return false
 }
 }
 let sig1 = secondTextField.rac_textSignal()
 .max(self.secondTextField, max: maxLength)
 .map{ next in
 if let str = next as? String {
 return str.characters.count > 0
 } else {
 return false
 }
 }
 let combined = RACSignal.combineLatest([sig0, sig1])
 combined.subscribeNext { (obj: AnyObject!) -> Void in
 let tup = obj as! RACTuple
 let valid = (tup.first as! Bool) && (tup.second as! Bool)
 self.button.enabled = valid
 }

Answer 1

I'm familiar with RxSwift, not RAC. :-( That said, I think I can say something constructive about this code...

sig0 and sig1 need more descriptive names.

I would be inclined to break up the combined.subscribeNext function. Something more like:

let buttonEnabled = RACSignal.combineLatest([sig0, sig1])
 .map { obj in 
 let tup = obj as! RACTuple // Wow RAC doesn't return type safe values?
 return (tup.first as! Bool) && (tup.second as! Bool)
 }
buttonEnabled.subscribeNext { obj in 
 let valid = obj as! Bool
 self.button.enabled = valid 
}

I strongly suspect that there is a function for mapping the buttonEnabled signal directly to the button though, maybe with an Action? You should look into that.

• Chris: This looks like a good solution, thanks! I've actually moved to RxSwift since this question because I found it to work much better with Swift