Dynamic appearance

appearence.swift

extension String {
    func capitalizingFirstLetter() -> String {
        return prefix(1).uppercased() + self.dropFirst()
    }
    
    mutating func capitalizeFirstLetter() {
        self = self.capitalizingFirstLetter()
    }
}

struct AppearenceStyle{
    let component:String
    var properties:[String:Any] = [:]
    
    init(component:String) {
        self.component = component;
    }
    
    mutating func add(property:String, withValue value:Any){
        self.properties[property] = value
    }
}

class AppearenceManager{
    init(styles:[AppearenceStyle]){
        
        for style in styles{
            if let appearenceClass = NSClassFromString(style.component) as? AnyObject {
                let appearence = getAppearenceReference(fromComponent: appearenceClass)!
                self.applyStyle(appearence: appearence, styles: style.properties)
            }
        }
    }
    
    private func applyStyle(appearence:AnyObject, styles:[String:Any]){
        for (property, value) in styles{
            let selector = Selector("set\(property.capitalizingFirstLetter()):")
            print(appearence, selector, value)
            appearence.performSelector(onMainThread: selector, with: value, waitUntilDone: true)
        }
    }
    
    private func getAppearenceReference(fromComponent:AnyObject)->AnyObject?{
        let appearenceSelector = Selector("appearance")
        return fromComponent.perform(appearenceSelector)?.takeUnretainedValue() as? AnyObject
    }
}

//Usage
var uiLabelStyle = AppearenceStyle(component: "UILabel");
uiLabelStyle.add(property: "textColor", withValue: UIColor.blue);
uiLabelStyle.add(property: "backgroundColor", withValue: UIColor.yellow);

let styles = [uiLabelStyle]

let appearenceManager = AppearenceManager(styles: styles)