这个或那个在Swift中使用UIButton的点击

Question

我使用单个按钮显示登录字段。如果我们点击一​​次，登录视图移动左侧，将显示注册视图，然后，如果我们再次点击，注册视图将向右移动，将显示登录视图。我的编码如下。但是动画不起作用。请指导我。

var bottom_click : Bool = true

@IBAction func not_member_button(sender: UIButton) {

    if(bottom_click == false) {
        UIView.animateWithDuration(0.7, delay: 0.0, options: .CurveEaseOut, animations: {

            self.login_view.frame = CGRectMake(16, 150, 288, 187)
            self.crea_acc_view.frame = CGRectMake(370, 150, 288, 245)
            }, completion: { finished in

                //println("Basket doors opened!")
        })
        sender.titleLabel?.text = "Not a member? Sign Up" //Its not working. If we delete this, animation is working
        bottom_click = true
    }
    else {
        UIView.animateWithDuration(0.7, delay: 0.0, options: .CurveEaseOut, animations: {

            self.login_view.frame = CGRectMake(-500, 150, 288, 187)
            self.crea_acc_view.frame = CGRectMake(16, 150, 288, 245)
            }, completion: { finished in

                //println("Basket doors opened!")
        })
        sender.titleLabel?.text = "Already member? Login" // Its is not working. If we delete this, animation is working
        bottom_click = false
    }

}