Timer extension which breaks the retain cycle in Swift3

timer_break_retain.swift

// coming form https://gist.github.com/onevcat/2d1ceff1c657591eebde, adapt swift3
private class Block<T> {
    let f : T
    init (_ f: T) { self.f = f }
}

extension Timer {
    static func xxx_scheduledTimer(timeInterval ti: TimeInterval, repeats: Bool, block: ()->()) -> Timer {
        return self.scheduledTimer(timeInterval: ti, target: self, selector: #selector(xxx_blcokInvoke), userInfo: Block(block), repeats: repeats)
    }
    
    static func xxx_blcokInvoke(timer: Timer) {
        if let block = timer.userInfo as? Block<()->()> {
            block.f()
        }
    }
}