如何在 Swift 中增加字符串

Question

我需要按字母顺序保存文件。
现在我的代码正在按数字顺序保存文件

1.png
2.png
3.png
...

问题是当我再次阅读此文件时，我按照此处所述阅读了此文件

所以我正在考虑更改代码并不按数字顺序而是按字母顺序保存文件，如下所示：

a.png
b.png
c.png
...
z.png
aa.png
ab.png
...

但在 Swift 中，即使是字符类型也很难增加。
我该如何开始：

var s: String = "a"

并以这种方式增加s ？

Answer 1

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将此代码粘贴到 Playground 中并检查结果。n支持数字意味着您可以输入任何大数字，例如 99999999999999 享受吧！

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您可以取消注释for loop代码来检查代码是否正常工作\n但不要忘记为counter变量分配较小的值，否则 Xcode 将冻结。

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var fileName:String = ""\nvar counter = 0.0\nvar alphabets = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]\nlet totalAlphaBets = Double(alphabets.count)\nlet numFiles = 9999\n\n\nfunc getCharacter(counter c:Double) -> String {\n\n    var chars:String\n    var divisionResult = Int(c / totalAlphaBets)\n    let modResult = Int(c.truncatingRemainder(dividingBy: totalAlphaBets))\n\n    chars = getCharFromArr(index: modResult)\n\n    if(divisionResult != 0){\n\n        divisionResult -= 1\n\n        if(divisionResult > alphabets.count-1){\n            chars = getCharacter(counter: Double(divisionResult)) + chars\n        }else{\n            chars = getCharFromArr(index: divisionResult) + chars\n        }\n    }\n\n    return chars\n}\n\nfunc getCharFromArr(index i:Int) -> String {\n    if(i < alphabets.count){\n        return alphabets[i]\n    }else{\n        print("wrong index")\n        return "\xef\xa3\xbf"\n    }\n}\n\nfor _ in 0...numFiles {\n    fileName = getCharacter(counter: counter)+".png"\n    print(fileName)\n    counter += 1\n}\n\nfileName = getCharacter(counter: Double(numFiles))+".png"\nprint(fileName)\n

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