Swift中String字符串的操作切割、转Character、Character转Int、String转Array、Array转String

1.String的切割

例如：

let name: String = "zhangsan"
// 1.获取下标,从开始位置'z',往后移动一个位置,就是'h'的位置了
let subIndex = name.index(name.startIndex,offsetBy: 1)
let subIndex2 = name.index(name.startIndex,offsetBy: 4)

// 2.根据下标获取某个字符
let subStr = name[subIndex] //Character类型: h

// 3.获取中间某部分字符串
let midStr = name[subIndex...subIndex2]  // hang

// 4.获取前面某部分
let preStr = name[...subIndex] // zh

// 5.获取后面某部分
let posstr = name[subIndex...] // hangsan

吐槽，实在是太难用了，我们写个扩展吧

extension String {
    func mySubString(_ index1: Int,_ index2: Int) -> String {
        let subIndex1 = self.index(self.startIndex,offsetBy: index1)
        let subIndex2 = self.index(self.startIndex,offsetBy: index2)
        
        return String(self[subIndex1...subIndex2])
    }
    
    func getCharat(_ index: Int) -> Character {
        let subIndex = self.index(self.startIndex,offsetBy: index)
        
        return self[subIndex]
    }
}

使用：

let name: String = "zhangsan"
let str1 = name.mySubString(0,1)
let char1 = name.getCharat(2)
print("char1",char1) // char1 a
print("str1",str1) // str1 zh

2.Character和Int互相转换

let c: Character = "B
let value = Int(c.asciiValue!)
print(value) // 66
        
let num = 66
let char: Character = Character(UnicodeScalar(num)!)
print(char) // B

let value: UInt32 = String(subStr).unicodeScalars.first!.value

吐槽，这也太啰嗦了吧，自己写个扩展

extension Character {
    func toInt() -> Int {
        return Int(String(self).unicodeScalars.first!.value)
    }
}

使用:

let value2 = subStr.toInt()

3.String 和 Array的转换

在一些场景中，操作String，不如操作Array方便，操作完之后，再转回String

let arr = Array(name)
print(arr)

let arrStr = String(arr[0...4])
print(arrStr)

4. String的补充操作

a> 根据下标，截取子字符
b> 移除第一个子字符
c> 移除所有的子字符
d> 是否包含某个子字符
e> 重复的最多的字母

extension String {
    /**
     根据下标，截取子字符
     */
    func subStr(_ start: Int,_ end: Int) -> String {
        let startIdx = self.index(self.startIndex,offsetBy: start)
        let endIdx = self.index(self.startIndex,offsetBy: end)
        return String(self[startIdx...endIdx])
    }
    
    /**
     移除第一个子字符
     */
    func removeFirstSubStr(_ subStr: String) -> String {
        if subStr.count > self.count {
            return self
        }
        
        let len = subStr.count
        for i in 0..<self.count {
            let start = i
            let end = i + len - 1
            
            if end > self.count - 1 { // 防止数组越界
                break
            }
            if subStr == self.subStr(start,end) {
                if i == 0 && end == self.count - 1 { // 前后完全覆盖
                    return ""
                } else if i == 0 && end < self.count - 1 { // 从0开始覆盖前面一部分
                    return self.subStr(end + 1,self.count - 1)
                } else if i > 0 && end == self.count - 1 { // 从结尾覆盖后面一部分
                    return self.subStr(0,i - 1)
                } else { // 中间
                    let preStr = self.subStr(0,i - 1)
                    let trailStr = self.subStr(end + 1,self.count - 1)
                    return preStr + trailStr
                }
            }
        }
        
        return self
    }
    
    /**
     移除所有的子字符
     */
    func removeAllSubStr(_ subStr: String) -> String {
        var temp = self
        
        while temp.isContainSubStr(subStr) {
            temp = temp.removeFirstSubStr(subStr)
        }
        
        return temp
    }
    
    /**
         是否包含某个子字符
     */
    func isContainSubStr(_ subStr: String) -> Bool {
        let len = subStr.count
        for i in 0..<self.count {
            let start = i
            let end = i + len - 1
            if end > self.count - 1 {
                break
            }
            if subStr == self.subStr(start,end) {
                return true
            }
        }
        
        return false
    }
    
	/**
     重复的最多的字母
     */
    func getRepeatMaxCountLetter() -> Character {
        let tempArr = self.components(separatedBy: " ").joined() // 去除空格再拼接字母
        let dict = tempArr.reduce(into: [:]) { partialResult,char in
            partialResult[char,default: 0] += 1
        }
        
        print("dict",dict)
        var res: Character = "a"
        var cnt = 0
        dict.map { (key,value) in
            if value > cnt {
                cnt = value
                let temp1 = key
                res = temp1
            }
        }
        
        return res
    }
    
}

var str = "hello world hello jack"
let sub1Str = str.subStr(1,3)
print(sub1Str) // ell

var res = str.removeFirstSubStr(sub1Str)
print(res) // ho world hello jack

var temp = "hello world hello jack hello world hello jack hello world hello jack"
let res1 = temp.removeAllSubStr(sub1Str)
print(res1) // ho world ho jack ho world ho jack ho world ho jack