我试图在Swift中创建一个NSTimer，但我遇到了一些麻烦。
NSTimer(timeInterval: 1, target: self, selector: test(), userInfo: nil, repeats: true)
Test()是同一个类中的一个函数。
我在编辑器中得到一个错误:
无法找到一个超载的'init'接受提供的 参数
当我把selector: test()改为selector: nil时，错误就消失了。
我试过了:
选择器:测试() 选择器:测试 选择器:选择器(测试())
但是什么都没用，我在参考文献中找不到解决方案。
当前回答
// for swift 2.2
// version 1
buttton.addTarget(self, action: #selector(ViewController.tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(ViewController.tappedButton2(_:)), forControlEvents: .TouchUpInside)
// version 2
buttton.addTarget(self, action: #selector(self.tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(self.tappedButton2(_:)), forControlEvents: .TouchUpInside)
// version 3
buttton.addTarget(self, action: #selector(tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(tappedButton2(_:)), forControlEvents: .TouchUpInside)
func tappedButton() {
print("tapped")
}
func tappedButton2(sender: UIButton) {
print("tapped 2")
}
// swift 3.x
button.addTarget(self, action: #selector(tappedButton(_:)), for: .touchUpInside)
func tappedButton(_ sender: UIButton) {
// tapped
}
button.addTarget(self, action: #selector(tappedButton(_:_:)), for: .touchUpInside)
func tappedButton(_ sender: UIButton, _ event: UIEvent) {
// tapped
}
其他回答
选择器是Objective-C中方法名的内部表示。在Objective-C中，“@selector(methodName)”会将一个源代码方法转换为SEL的数据类型。因为你不能在Swift中使用@selector语法(里克斯特就在这里)，你必须手动指定方法名直接作为String对象，或者通过传递String对象给Selector类型。这里有一个例子:
var rightBarButton = UIBarButtonItem(
title: "Logout",
style: UIBarButtonItemStyle.Plain,
target: self,
action:"logout"
)
or
var rightBarButton = UIBarButtonItem(
title: "Logout",
style: UIBarButtonItemStyle.Plain,
target: self,
action:Selector("logout")
)
选择器在Swift 4:
button.addTarget(self, action: #selector(buttonTapped(sender:)), for: UIControlEvents.touchUpInside)
使用#selector将在编译时检查代码，以确保要调用的方法确实存在。更好的是，如果方法不存在，你会得到一个编译错误:Xcode将拒绝构建你的应用，从而消除另一个可能的错误来源。
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.rightBarButtonItem =
UIBarButtonItem(barButtonSystemItem: .Add, target: self,
action: #selector(addNewFireflyRefernce))
}
func addNewFireflyReference() {
gratuitousReferences.append("Curse your sudden but inevitable betrayal!")
}
下面是一个关于如何在Swift上使用Selector类的快速示例:
override func viewDidLoad() {
super.viewDidLoad()
var rightButton = UIBarButtonItem(title: "Title", style: UIBarButtonItemStyle.Plain, target: self, action: Selector("method"))
self.navigationItem.rightBarButtonItem = rightButton
}
func method() {
// Something cool here
}
请注意，如果作为字符串传递的方法不起作用，它将在运行时失败，而不是在编译时失败，并使应用程序崩溃
// for swift 2.2
// version 1
buttton.addTarget(self, action: #selector(ViewController.tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(ViewController.tappedButton2(_:)), forControlEvents: .TouchUpInside)
// version 2
buttton.addTarget(self, action: #selector(self.tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(self.tappedButton2(_:)), forControlEvents: .TouchUpInside)
// version 3
buttton.addTarget(self, action: #selector(tappedButton), forControlEvents: .TouchUpInside)
buttton.addTarget(self, action: #selector(tappedButton2(_:)), forControlEvents: .TouchUpInside)
func tappedButton() {
print("tapped")
}
func tappedButton2(sender: UIButton) {
print("tapped 2")
}
// swift 3.x
button.addTarget(self, action: #selector(tappedButton(_:)), for: .touchUpInside)
func tappedButton(_ sender: UIButton) {
// tapped
}
button.addTarget(self, action: #selector(tappedButton(_:_:)), for: .touchUpInside)
func tappedButton(_ sender: UIButton, _ event: UIEvent) {
// tapped
}
