字符
正式介紹字符串之前呢，需要引入一個(gè)新的數(shù)據(jù)類型游岳，即字符（Character）班缎，字符類型只能存放一個(gè)字符，例如：
var ch : Character = "!"
單獨(dú)的一個(gè)字符可以拼接在一個(gè)字符串的后面揣非，具體方法如下：
var str = "Hello, playground"
str.append(ch)
字符串
//常量字符串抡医，不能對(duì)其進(jìn)行重新賦值或者拼接等操作
let str2 = "I'm an immutable string"
//可變字符串
var str = "你好, playground"
//字符串的拼接
str += "\u{1F496}"
//初始化一個(gè)空的字符串
//方法一
var emptyString = ""
//方法二 實(shí)際上是創(chuàng)建了一個(gè)字符串類的對(duì)象
var anotherEmptyString = String()
//判斷當(dāng)前字符串是否為空,返回的是一個(gè)Bool類型
str.isEmpty
//字符串的遍歷
for c in str.characters
{
print(c)
}
//計(jì)算字符串的長(zhǎng)度
str.characters.count
//字符串的插值 String Interpolation
let imInt:Int = 2
let imTouble:(Bool,Float) = (true,1.1435926)
print("\(imInt),\(imTouble.0)")
//輸出結(jié)果為：2,true
//字符串的比較
let str_a = "abc"
let str_b = "abc"
str_a == str_b //true
let str_c = "abd"
str_a < str_c //true
let str_d = "abcd"
str_c < str_d //false
//前綴和后綴的判斷
str.hasPrefix("http") //false
str.hasSuffix("playground") //true
//import Foundation以后就可以用String來(lái)使用OC中NSString中的所有方法
import Foundation
// 下面的大小寫轉(zhuǎn)換的方法均不改變str本身的值
//把字符串中的每一個(gè)單詞的首字母都轉(zhuǎn)換成大寫
str.capitalized
//把字符串中所有的字符轉(zhuǎn)換成大寫
str.uppercased()
//把字符串
str.lowercased()
//trim操作，即對(duì)字符串頭尾中沒(méi)有用的字符進(jìn)行截取早敬，只保留中間有用的部分
var str3 = " !so cool "
str3.trimmingCharacters(in: NSCharacterSet.whitespaces) //!so cool
str3.trimmingCharacters(in: NSCharacterSet.init(charactersIn: " !") as CharacterSet)//so cool
//字符串的分割：把字符串按某個(gè)字符或字符串截取成一個(gè)一個(gè)的單詞
var str4 = "welcom to play"
str4.components(separatedBy: " ") //["welcom", "to", "play"]
str4 = "welcoom to play swift!Step-by-step learn from now"
str4.components(separatedBy: NSCharacterSet.init(charactersIn: " !-") as CharacterSet)//["welcoom", "to", "play", "swift", "Step", "by", "step", "learn", "from", "now"]
//join 字符串的連接
var arry = ["a","b","c"]
let res = arry.joined(separator: "_") //"a_b_c"
//查找字符串中某個(gè)字符穿出現(xiàn)的范圍
str4.range(of:"play")
str4.range(of: "welcom", options: String.CompareOptions.caseInsensitive)//忽略大小寫進(jìn)行查找
str4.startIndex
str4.endIndex
//截取字符串
let startIndex:String.Index = str4.startIndex
let endIndex:String.Index = str4.index(str4.startIndex, offsetBy: 8)
//下面的寫法在swift 3.0中是錯(cuò)誤的
//let strRange = Range<String.Index>(start:startIndex,end:endIndex)
//swift 3.0中的正確寫法為
let strRange = startIndex ..< endIndex
str4.substring(with: strRange) //"welcome t"
str4.substring(to: endIndex) //"welcome t"
str4.substring(from: startIndex)
//插入字符串
var insertIndex = str4.index(str4.startIndex, offsetBy: 2)
str4.insert("!", at: insertIndex)
//刪除字符
str4.remove(at: insertIndex)
str4.removeSubrange(strRange)
//替換字符串
str4.replaceSubrange(strRange, with: "hello")
關(guān)于字符串的更多操作后續(xù)補(bǔ)充忌傻，可參考這里
