//不可變字符串
let a = "123"
//可變字符串
var b = "456"
b = "666"
三、字符串的長(zhǎng)度
//字符串長(zhǎng)度
let aa = "123a旺旺"
//按字節(jié)的長(zhǎng)度功咒，一個(gè)漢字占三個(gè)字節(jié)
aa.lengthOfBytes(using: String.Encoding.utf8) //10
//按字符個(gè)數(shù)
aa.characters.count //6
//aa.characters 可當(dāng)數(shù)組使用
for i in aa.characters {
print(i)
}
四愉阎、字符串的拼接
let aa = "123a旺旺"
let bb = "xyz"
bb + aa //"xyz123a旺旺"
let cc = 123
bb + "\(cc)" //"xyz123"
五悼嫉、字符串格式化
let dd = 144
let ddd = String(format: "%02d:%02d", dd/60, dd%60) //"02:24"
六幻捏、字符串的截取
let ee = "Hello,World"
let startI = ee.startIndex
let secondI = ee.index(after: startI)
ee.substring(from: secondI) //"ello,World"
ee //"Hello,World"
let endI = ee.endIndex
let middleI = ee.index(endI, offsetBy: -6)
ee.substring(to: middleI) //"Hello"
let range:Range<String.Index> = startI..<middleI
ee.substring(with: range) //"Hello"
ee.substring(with: secondI..<endI) //"ello,World"
ee //"Hello,World"
所有的截取都不會(huì)改變?cè)?/li>
七渴肉、字符串的替換
var ff = "World,Hello"
let sIndex = ff.startIndex
let mIndex = ff.index(sIndex, offsetBy: 5)
let range2 = sIndex...mIndex
ff.replaceSubrange(range2, with: "123") //"123Hello"
ff //"123Hello"
