swift 字符串的截取 以及 Range 的用法

func someMethodOfRange() {

        //1.截取字符串（字符）在整个字符串中所在的位置，返回的类型为 Index

        var str = "abcdefghi"

        let startIndex =  str.rangeOfString("cde")!.startIndex

        print(startIndex)//2

        let endIndex =  str.rangeOfString("cde")!.endIndex

        print(endIndex)//5

        //2、根据字符串的索引来获取对应的字符

        let text = "abcdefghi"

        let index2 = text.startIndex.advancedBy(2) //will call succ 2 times

        print(index2)//2

        let lastChar: Character = text[index2] //now we can index!

        print(lastChar)//c

        let lastChar2 = text.characters[index2] //will do the same

        print(lastChar2)//c

        //3.截取字符串（字符）在整个字符串中所在的范围 、返回值类型 Range<Index>

        let range: Range<String.Index> = text.rangeOfString("bc")!

        print(range)//1..<3

        let index3: Int = text.startIndex.distanceTo(range.startIndex)

        print(index3)//1

        let index4: Int = text.startIndex.distanceTo(range.endIndex)

        print(index4)//3

        print(text.characters.count)//9

        let abc = "@救123"

        print(abc.characters.count)//5

//4.0 Index --> Int

let range: Range<String.Index> = self.text!.rangeOfString(text)!

        let index3: Int = self.text!.startIndex.distanceTo(range.startIndex)

        let index4: Int = self.text!.startIndex.distanceTo(range.endIndex)

        //一个字符串。指标值可以通过调用predecessor()方法访问其 先前 指标，其指标successor()下一个指标 调用方法。字符串中的任何指标可从任何其他指数通过把这些方法结合在一起，或通过使用--（_：）方法。试图访问一个字符串的范围以外的索引会引发一个运行时错误

        let greeting = "123456789"

        greeting[greeting.startIndex]

        print(greeting)

        print("起使位置\(greeting.startIndex)")//0

        print("终点位置\(greeting.endIndex)")//9

        print(greeting[greeting.startIndex])//1

        greeting[greeting.endIndex.predecessor()]

        print(greeting[greeting.endIndex.predecessor()])//9

        print(greeting.endIndex.predecessor())//8

        print(greeting.startIndex.successor())//1

        greeting[greeting.startIndex.successor()]

        print(greeting[greeting.startIndex.successor()])//2

        let index = greeting.startIndex.advancedBy(7)

        greeting[index]

        print(greeting[index])//8

        //试图在字符串的范围以外的索引处访问一个字符，将引发一个运行时错误。”

        //greeting[greeting.startIndex.predecessor()]//cuowu

        //print(greeting[greeting.endIndex])//cuowu

        //越界

        //greeting[greeting.endIndex]

        //greeting.endIndex.successor()

        //““Use the <indices> property of the <characters> property to 创建一个字符串中访问单个字符的所有索引的范围。”

        for index in greeting.characters.indices {

            print("\(greeting[index])",terminator: "")

            //            print("**")

        }

    }

//相关的应用：在UILabel里面，不同文本显示不同字体的大小

extension UILabel {

    func settingLabelTextKitWithText(text:String,font:UIFont) {

        if text.isEmpty {//通过检查其 Boolean 类型的 isEmpty 属性来判断该字符串是否为空：

            print("什么都没有")

            return

        }else {

            //方法1

            let attrstring:NSMutableAttributedString = NSMutableAttributedString(string: self.text!)

            let str = NSString(string: self.text!)

            let theRange = str.rangeOfString(text)

            attrstring.addAttribute(NSFontAttributeName, value: font, range: theRange)

            self.attributedText = attrstring

        }

    }