swift3.0的一些知识

import UIKit

//----------------- 字符串/字符 的定义 -----------------

//字符串变量

var str1 = "hello"

//字符串常量

let str2 = "swift3.0"

//声明为nil，

var str3:String?

//空字符串

let str4 = String()

//空字符串 提倡用这样的字面量声明,类型可不指定，swift自动识别

let str5 = ""

//字符

var char1:Character = "m"

//----------------- 字符串/字符 的拼接 -----------------

var p_str1 = str1+str2

p_str1 = String(format:"%@~%@",str1,str2)

p_str1 = String(format:"%@~%@-%d",str2,456)

//这种拼接方式方便地组合多种类型

p_str1 = "(str1)(str2)(456)"

p_str1 = "(str1)(str2)(char1)"

//在后面添加

p_str1.append(char1)

p_str1 += str2

//与数组的组合

var strArray = ["hello","swift","3.0"]

p_str1 = strArray.joined(separator: "-")//数组通过指定字符拼接

strArray = p_str1.components(separatedBy: "-")//拆分为数组

//枚举字符

for ch in p_str1.characters{

print(ch)

switch ch {

case "0":

print("有")

default:

break

}

}

//--- 获取字符串中指定索引处的字符 -----------

//字符串长度

p_str1.characters.count

//首字母

char1 = p_str1[p_str1.startIndex]

//末字母

char1 = p_str1[p_str1.index(before: p_str1.endIndex)]

//第二个字母

char1 = p_str1[p_str1.index(after: p_str1.startIndex)]

//索引4的字母

char1 = p_str1[p_str1.index(p_str1.startIndex,offsetBy: 4)]

//--- 获取字符串子串 -----------

let i = p_str1.index(p_str1.startIndex,offsetBy: 4)

let j = p_str1.index(p_str1.startIndex,offsetBy: 8)

var subStr = p_str1.substring(to: i)

subStr = p_str1.substring(from: i)

subStr = p_str1.substring(with: i..<j)

//通过扩展来简化一下

extension String {

subscript (range: Range<Int>) -> String {

get {

let startIndex = self.index(self.startIndex,offsetBy: range.lowerBound)

let endIndex = self.index(self.startIndex,offsetBy: range.upperBound)

return self[Range(startIndex..<endIndex)]

}

set {

let startIndex = self.index(self.startIndex,offsetBy: range.upperBound)

let strRange = Range(startIndex..<endIndex)

self.replaceSubrange(strRange,with: newValue)

}

}

}

subStr = p_str1[0..<14]

//通过指定字符串截取子串

let range1 = p_str1.range(of: "o-")

let range2 = p_str1.range(of: ".")

subStr = p_str1.substring(from: (range1?.upperBound)!)

subStr = p_str1.substring(with: (range1?.upperBound)!..<(range2?.lowerBound)!)

//插入、删除指定字符串

subStr.insert("!",at: subStr.startIndex)

subStr.endIndex)

subStr.insert(contentsOf:"YY".characters,at: subStr.index(after: subStr.startIndex))

subStr.insert(contentsOf:"MM".characters,at: subStr.index(before: subStr.endIndex))

let x = p_str1.index(p_str1.startIndex,offsetBy: 4)

subStr.remove(at: x)

subStr

subStr.remove(at: subStr.startIndex)

subStr

subStr.remove(at: subStr.index(after: subStr.startIndex))

subStr

subStr.remove(at: subStr.index(before: subStr.endIndex))

subStr

let ran1 = subStr.index(subStr.endIndex,offsetBy: -3)..<subStr.endIndex

subStr.removeSubrange(ran1)

subStr

let ran2 = subStr.index(subStr.startIndex,offsetBy: 4)..<subStr.endIndex

subStr.removeSubrange(ran2)

subStr

subStr = "http://baidu.com"

let ran3 = subStr.range(of: ":")

let ran4 = subStr.range(of: ".")

subStr.removeSubrange((ran3?.upperBound)!..<(ran4?.lowerBound)!)

subStr

//是否有前、后缀

p_str1.hasPrefix("3.0")

p_str1.hasSuffix("3.0")

//是否为空

p_str1.isEmpty

str3?.isEmpty

str4.isEmpty

str5.isEmpty

//--- 大小写转换 -----------

subStr = "ashdfasdjf"

subStr.capitalized

subStr.uppercased()

subStr.lowercased()

//--- 字符串比较 -----------

subStr = "2.6.2"

p_str1 = "2.6.1"

str1 = "2.7"

str3 = "2.7.0"

subStr > p_str1

subStr > str1

str1 == str3

str1 > str3!

str1 < str3!

//--- 字符串转换 -----------

Int(str1)

Double(str1)

Double(str3!)

Bool(str1)

str1 = "true"

Bool(str1)

（编辑：李大同）

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