xcode9.1，swift4.0
When I tried swift for the first time, when adding a response event to the button, I used the selector to repeatedly report an error
yourBtn.addTarget(self, action:"clickYourBtn", for: UIControlEvents.touchUpInside) , the error is as the title
yourBtn.addTarget(self, action:Selector("clickYourBtn"), for: UIControlEvents.touchUpInside)
yourBtn.addTarget(self, action:#selector(clickYourBtn), for: UIControlEvents.touchUpInside)
The third method can also be used directly in 3.2, but an error will be reported in 4.0, and @objc needs to be added before the method
About selector recommend this article https://www.jianshu.com/p/f3f2c663115d
I have seen that @objc cannot be overused (this article https://www.jianshu.com/p/b50a8ed6a00b)