swift4字符串截取实用方法

1.contains方法应用（可用于是否字符串是否包含另一个字符串）：

let str1 = "josh"
let str2 = "joshwang"
str1.contains(str2)   //false
str2.contains(str1)   //true

2.append方法应用：

var resultArray: [String] = []
resultArray.append(contentsOf: [str1, str2,"123456"])
resultArray.append("hahahaha")
print(resultArray)
输出结果：["josh", "joshwang", "123456", "hahahaha"]

3.字符串范围截取操作

var str = "Hello, joshwang0830"
var index = str.index(of: ",")//得到“,”在字符串中的位置
let str3 = str[index!...]//获取","后的所有字符（包括",")
 
//Swift 3.0
let greeting = str[str.startIndex..<index!]//获取","前的所有字符(不包括",")
let index2 = str.index(index!, offsetBy: 2)  //空格位置往后移动2位
let name = str[index2 ..< str.endIndex]  //joshwang0830
//Swift 4.0
//得到hello
let greetings = str.prefix(upTo: index!)
let greetingss = str[..<index!]
 
//空格位置往后移动2位
let index3 = str.index(index!, offsetBy: 2)

//joshwang0830
let names = str.suffix(from: index3)
let namess = str[index3... ]

4.String 与 NSString 转换 需要遵循严格的类型转化

//String 与 NSString 转换  需要遵循严格的类型转化
var strString: NSString = str as NSString
var str4: String = String(strString)

5.字符串范围截取(prefix;suffix)常用于拼接后台返回的地址：

//字符串范围截取
let num = "123.45"
let deRange = num.range(of: ".")
 
//FIXME:按某个字符串截取
 
//截取小数点前字符(不包含小数点)  123
let wholeNumber = num.prefix(upTo: deRange!.lowerBound)
//截取小数点后字符(不包含小数点) 45
let backNumber = num.suffix(from: deRange!.upperBound)
//截取小数点前字符(包含小数点) 123.
let wholeNumbers = num.prefix(upTo: deRange!.upperBound)
//截取小数点后字符(包含小数点) .45
let backNumbers = num.suffix(from: deRange!.lowerBound)

6.删除与字符串替换

//FIXME:删除字符串中的某部分  Ho
var str5 = "Hello"
let startIndex = str.index(str.startIndex, offsetBy: 1)
let endIndex = str.index(str.startIndex, offsetBy: 3)
str5.removeSubrange(startIndex...endIndex)
//替换字符串  Hnewo
var sig = "H123456o"
sig.replacingCharacters(in: startIndex...endIndex, with: "123456")