@IBOutlet weak var button_0: UIButton!
@IBOutlet weak var button_1: UIButton!
@IBOutlet weak var button_2: UIButton!
@IBOutlet weak var button_3: UIButton!
//...以下複数個続く

var buttons:[UIButton] = []

buttons.append(button_0)
buttons.append(button_1)
buttons.append(button_2)
//...以下個数分続く
for i in 0..<buttons.count{
    buttons[i].tag = i
    buttons[i].addTarget(self, action: #selector(ToolView.action(_:)), forControlEvents: .TouchUpInside)
}

@objc private func action(sender: UIButton){
    switch sender.tag {
    case 0:
        print("button_0")
    case 1:
        print("button_1")
    case 2:
        print("button_2")
    //...個数分続く
    default:break
    }
}

@IBAction func action(sender: UIButton) {
    switch sender.tag {
    case 0:
        print("button_0")
    case 1:
        print("button_1")
    case 2:
        print("button_2")
    //...個数分続く
    default:break
    }
}

@IBOutlet var buttons:[UIButton] = []