Swift入门教程教程15-扩展(extension)

标签：swift   入门教程   扩展   extension   

extension SomeType {
// 
}

extension SomeType: SomeProtocol, AnotherProctocol {
// 协议实现写到这里
}

extension String {  
    //扩展下标脚本
    subscript (r: Range<Int>) -> String {  
        get {  
            let subStart = advance(self.startIndex, r.startIndex, self.endIndex) 
            let subEnd = advance(subStart, r.endIndex - r.startIndex, self.endIndex)  
            return self.substringWithRange(Range(start: subStart, end: subEnd))  
        }  
    }
    //扩展实例方法  
    func substring(#from: Int) -> String {  
        let end = countElements(self)  
        return self[from..<end]  
    }  
    func substring(#from: Int, length: Int) -> String {  
        let end = from + length  
        return self[from..<end]  
    }  
    func substring(#from:Int, to:Int) ->String  
    {  
        return self[from..<to]  
    }
    //定义新的构造器
    init(first:String,second:String)
    {
        self.init(first+second)
    }
    //定义新的嵌套类型，这里的嵌套类型是一个枚举
    //所谓嵌套类型，简单理解就是在一个类型里定义另一个类型
    enum Kind{
        case IsIntStr,NotIntStr
    }
    //定义一个新的实例变量，返回这个字符串是否是可以转换为Int
    var kind:Kind{
        var result:Kind = Kind.IsIntStr
        if self.toInt()? == nil{
            result = .NotIntStr
      	}
        return result	
    }
}  
var str = String(first:"hello ",second:"hwc") 
var str1 = str.substring(from:6)  //hwc
var str2 = str.substring(from:0,to:5)  //hello
var str3 = str.substring(from:0,length:5)//hello
var str4 = str[0...5] //hello
var strKind = str.kind //NotIntStr
if strKind == String.Kind.NotIntStr{
        println("Not an int string")
}

Swift入门教程教程15-扩展(extension)

标签：swift   入门教程   扩展   extension   

原文地址：http://blog.csdn.net/hello_hwc/article/details/41555225