Helpers.swift

public extension CollectionType {
    // MARK: Flatteners
    public func flatten(path: (Self.Generator.Element) -> [Self.Generator.Element]) -> [Self.Generator.Element] {
        guard !self.isEmpty else { return [] }
        return self + self.flatMap { path($0).flatten(path) }
    }
}

public extension UIView {
    // MARK: Properties
    public var flatSubviews: [UIView] {
        return self.subviews.flatten { $0.subviews }
    }
    
    public var flatConstraints: [NSLayoutConstraint] {
        return (self.flatSubviews + [self]).flatMap { $0.constraints }
    }
}