swift 4.0 类型扩展 类扩展

import UIKit



class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        /*
         掉用类型扩展
        var hello = "hi"
        hello.sayHello()
        var newInt = 30
        print(newInt.squared)
        print(9999.squared)
        */
        var whoisLisa = Lisa()
        print(whoisLisa.lisa)
        
        var whoisLisa2 = Lisa()
        print(whoisLisa.lisa)
        print(whoisLisa2.describleYousele())
        
    }

}
//类型扩展
extension String {
    func sayHello() {
        print("say hello")
    }
}

extension Int {
    var squared: Int {
        return self*self
    }
}

//类扩展
class Lisa {
    var lisa = "lisa is a angle"
}
extension Lisa {
    func describleYousele() -> String {
        return "my name is lisa then always say \(lisa)"
    }
}