iOS SwiftUI-1 字串處理

1.字串分割
2.字串擷取
3.檢查字串
4.判斷前與後字串
5.大小寫轉換
6.搜尋字串，在...之前、在...之後的字符
7.搜尋字串範圍
8.字串串接
9.指定位置插入字符
10.字串範圍修改
11.刪除範圍內的字串，與字首、字尾
12.字串翻轉
13.字串遍歷
14.字串過濾
15.reduce用法

1. 字串分割

   //分割字串
    let stringSplit = self.path.split(separator: "/")
    //如果數量是0，則存入""，否則存入最後一筆
    let string = stringSplit.count == 0 ? "" : String(format: String(stringSplit[stringSplit.count-1]))
   

2. 字串擷取

    let str = "20200101170520.MP4"
    let index = str.index(str.startIndex, offsetBy: 5)
    let str01 = str[..<index]//20200
    let str02 = str[...index]//202001
    let str03 = str[index...]//101170520.MP4
   

    let path = "20200101170520.MP4"
    //設定index範圍，path.endIndex由右側開始，檢查長度大於4則以-4，否則不偏移，不做此判斷可能導致閃退
    let index = path.index(path.endIndex, offsetBy:  path.count > 4 ? -4 : 0)
   
    //prefix由左側開始擷取到index，upTo是指不包含-4那個位置
    //path_removeExtension = 20200101170520
    let path_removeExtension = String(path.prefix(upTo: index))
   
    //prefix由左側開始擷取到index，upTo是指包含-4那個位置
    //path_removeExtension = 20200101170520.
    let path_removeExtension = String(path.prefix(through: index))
   
    //prefix由左側開始擷取到5
    //path_removeExtension = 20200
    let path_removeExtension = String(path.prefix(5))
   
    //設定index範圍，path.startIndex由左側開始，檢查長度大於4則以4，否則不偏移，不做此判斷可能導致閃退
    let index = path.index(path.startIndex, offsetBy: path.count > 4 ? 4 : 0)
   
    //prefix由右側開始擷取到index，包含4那個位置
    //path_removeExtension = 0101170520.MP4
    let path_removeExtension = String(path.suffix(from: index))
   
    //prefix由右側開始擷取5個
    //path_removeExtension = 0.MP4
    let path_removeExtension = String(path.suffix(5))
   

3. 檢查字串
   要判斷是否是空可以使用

    let str = "123"
    var isEmptyFlag = false
    if str.isEmpty {
        //未成立
        isEmptyFlag = true
    }
    //isEmptyFlag = false 判斷不為空
   

   判斷字串長度

    let str = "sssss"
    print("str.count \(str.count)") //str.count = 5
   

4. 判斷前與後字串

    let str = "Hoooooo Prrrrr"
    var hasPrefix = false
    if str.hasPrefix("Hoooooo") {
        hasPrefix = true
    }
    //hasPrefix = true，在字首找到對應的字串
   

    let str = "Hoooooo Prrrrr"
    var hasSuffix = false
    if str.hasSuffix("Prrrrr") {
        hasSuffix = true
    }
    //hasSuffix = true，在字尾找到對應的字串
   

5. 大小寫轉換

    let str = "HooPPOOO Prrrrr"
    str.uppercased()//全部大小
    str.lowercased()//全部小寫
    str.capitalized//字首大寫
   

6. 搜尋字串，在...之前、在...之後的字符

    let str = "20200101170520.MP4"
    let str01 = str[str.index(after: str.startIndex)]//0
    let str02 = str[str.index(before: str.endIndex)]//4
   

7. 搜尋字串範圍

    let str = "20234101170520.MP4"
    let str01 = str.range(of: "202341")
    //如果有搜尋到str01不為nil，且可以取得lowerBound與upperBound
   

8. 字串串接

    var str = "20234101170520.MP4"
    str.append("Video")
   

9. 指定位置插入字符

    var str = "20234101170520.MP4"
    let str01 = str.range(of: "10117")
    if let upper = str01?.upperBound {
        //插入單一字符
        str.insert("P", at: upper)//2023410117P0520.MP4
    }
    str = "20234101170520.MP4"
    if let lower = str01?.lowerBound {
        //插入單一字符
        str.insert("P", at: lower)//20234P101170520.MP4
    }
   
    var str = "20234101170520.MP4"
    let str01 = str.range(of: "10117")
    if let upper = str01?.upperBound {
        //插入多個字符
        str.insert(contentsOf: "Pa", at: upper)
    }
    str = "20234101170520.MP4"
    if let lower = str01?.lowerBound {
        //插入多個字符
        str.insert(contentsOf: "Pa", at: lower)
    }
   

10. 字串範圍修改

    var str = "20234101170520.MP4"
    str.replaceSubrange(str.startIndex..<str.index(str.startIndex, offsetBy: 4), with: "Apple")
    //Apple4101170520.MP4
    

11. 刪除範圍內的字串，與字首、字尾

    var str = "20234101170520.MP4"
    str.removeSubrange(str.startIndex..<str.index(str.startIndex, offsetBy: 4))
    //4101170520.MP4
    
    var str = "20234101170520.MP4"
    //刪除字首
    let str01 = str.dropFirst()//0234101170520.MP4
    //刪除兩個字首
    let str02 = str.dropFirst(2)//234101170520.MP4
    //刪除字尾
    let str03 = str.dropLast()//20234101170520.MP
    //刪除兩個字尾
    let str04 = str.dropLast(2)//20234101170520.M
    

12. 字串翻轉

    var str = "20234101170520.MP4"
    let str01 = String(str.reversed())//4PM.02507110143202
    

13. 字串遍歷

    //方法1
    var str = "20234101170520.MP4"
    for i in str {
        print(i)
    }
    //方法2
    str.forEach { char in
        print(char)
    }
    
    //方法3
    str.map { char in
        print("char \(char)")
    }
    

14. 字串過濾

    var str = "20234101170520.MP4"
    
    let str01 = str.filter {
        $0 == "2" || $0 == "0"
    }
    //2020020
    

15. reduce用法

    var str = "20234101170520.MP4"
    
    let str01 = str.reduce("Array", {(resulut,char) -> String in
        print("\(resulut + String(char))")
        /*
        Array2
        Array20
        Array202
        Array2023
        Array20234
        Array202341
        Array2023410
        Array20234101
        Array202341011
        Array2023410117
        Array20234101170
        Array202341011705
        Array2023410117052
        Array20234101170520
        Array20234101170520.
        Array20234101170520.M
        Array20234101170520.MP
        Array20234101170520.MP4
        */
        return resulut + String(char)
    })
    //str01最後是 Array20234101170520.MP4