Swift4 字符串的修改

一、遍历characters，在swift4中characters属性被弃用

• 之前

let stringA = "Stay Foolish, Stay Hungry"
for character in stringA.characters{
    print(character)
}

• swift4

let stringA = "Stay Foolish, Stay Hungry"
for character in stringA{
    print(character)
}

二、count

• 之前

let stringA = "秋水共长天一色"
srtingA.character.count     // 7

• swift4

let stringA = "秋水共长天一色"     
stringA.count               // 7
stringA.utf8.count          // 21
stringA.utf16.count         // 7

三、substring

关于什么是substring 我来告诉你，点我！

• 之前

let stringA = "<<>>"
let indexStartOfText = stringA.index(stingA.startIndex, offsetBy:3)
let indexEndOfText = stringA,index(stringA.endIndex, offsetBy:-3)

let subString1 = stringA.substring(from: indexStartOfText) // "Hello>>>"
let subString2 = stringA.substring(to: indexEndOfText) // "<<
let subString3 = stringA.substring(with: indexStartOfText..// "Hello"

• swift4

let stringA = "<<>>"
let indexStartOfText = stringA.index(stingA.startIndex, offsetBy:3)
let indexEndOfText = stringA,index(stringA.endIndex, offsetBy:-3)

let subString1 = stringA[indexStrtOfText...] // "Hello>>>"
let subString2 = stringA[..EndOfText]  // "<<
let subString3 = stringA[indexStartOfText..EndOfText] // "Hello"

• swift4使用prefix/suffix方法

let stringA = "0123456789"
let index4 = stringA.index(stringA.startIndex, offsetBy: 4)

// The first of each of these examples is preferred
stringA[...index4]              // "01234"
stringA.prefix(through: index4)

stringA[.."0123"
stringA.prefix(upTo: index4)

stringA[index4...]              // "456789"
stringA.suffix(from: index4)

• Substring->Sting

let string1 = String(substring1)

四、”“”string”“”控制多行文本输出

let stringA = """
关关雎鸠，
在河之洲，
窈窕淑女，
君子好逑，
"""

也可以控制开头的空格

let stringA = """
    予观夫巴陵胜状，在洞庭一湖。衔远山，吞长江，浩浩汤汤，横无际涯；朝晖夕阴，气象万千。此则岳阳楼之大观也，前人之述备矣。然则北通巫峡，南极潇湘，迁客骚人，多会于此，览物之情，得无异乎？
"""