pick.swift

// Pick

public extension SignalProducer where Value: OptionalProtocol {
    func pick<T>(picking: @escaping ((Value.Wrapped) -> (SignalProducer<T?, Error>))) -> SignalProducer<T?, Error> {
        return self.flatMap(.latest) { value -> SignalProducer<T?, Error> in
            if let value = value.optional {
                return picking(value)
            } else {
                return SignalProducer<T?, Error>(value: nil)
            }
        }
    }
}


// Usage

class LayerTableCellView: NSTableCellView {
    
    // Views
    @IBOutlet var label: NKLabel!
    
    
    // Models
    internal let config = MutableProperty<ChartConfigModel?>(nil)
    
    
    override func awakeFromNib() {
        let title = config.producer.pick { $0.reactive.title.producer }
        label.reactive.text <~ title.map { $0 ?? "" }
    }
    
    func setConfig(_ config: ChartConfigModel) {
        self.config.value = config
    }
}