最近在回答StackOverflow的问题时，发现performSelector方法在Swift被去掉，Apple的注释是这个方法被去掉是因为不安全：
NOTE
The performSelector: method and related selector-invoking methods are not imported in Swift because they are inherently unsafe.
如果在Swift调用这个方法会编译出错：
'performSelector' is unavailable: 'performSelector' methods are unavailable
方法一：反复尝试后，我发现可以使用 UIControl：
func sendAction(_ action: Selector, to target: AnyObject!, forEvent event: UIEvent!)
下面是一段演示代码：
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
var control:UIControl = UIControl()
control.sendAction(Selector("greetings"), to: self, forEvent: nil)
}
func greetings() {PRintln("greetings world")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
Log打印出：
greetings world
如果是Swift调用Objective-C类的target和action，可以参考下面的例子，假设有TestClass是Objective-C类，并且有getBarButtonItem返回UIBarButtonItem：
#import "TestClass.h"
@implementation TestClass
- (UIBarButtonItem *)getBarButtonItem
{
UIBarButtonItem *bar = [[UIBarButtonItem alloc] init];
bar.target = self;
bar.action = @selector(help);
return bar;
}
- (void)help
{
NSLog(@"Help offered");
}
@end
那么在Swift里可以用下面的代码执行help方法：
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
var testClass = TestClass()
var button: UIButton = UIButton()
var barButtonItem = testClass.getBarButtonItem()
button.sendAction(barButtonItem.action, to: barButtonItem.target, forEvent: nil)
}
}
Log打印出：
2014-07-06 23:49:49.942 TestApp [53986:2552835] Help offered
方法二：可以使用NSThread.detachNewThreadSelector，好处是可以使用延迟，并且可以附带object，下面是掩饰代码：
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let delay = 2.0 * Double(NSEC_PER_SEC)
var time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue(), {
NSThread.detachNewThreadSelector(Selector("greetings:"), toTarget:self, withObject: "sunshine")
})
}
func greetings(object: AnyObject?) {
println("greetings world")
println("attached object: \(object)")
}
}
方法三：使用NSTimer:
class func scheduledTimerWithTimeInterval(_ seconds: NSTimeInterval,
target target: AnyObject!,
selector aSelector: Selector,
userInfo userInfo: AnyObject!,
repeats repeats: Bool) -> NSTimer!
Xcode 6 Beta2
另外请参考一篇不错的文章：初探swift语言的学习笔记十一(performSelector)
作者：Yang Zhou
出处：http://yangzhou1030.cnblogs.com
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