Swift 3：快速文件路径分离

Question

我需要为数千个文件分割文件路径的一部分。所以我需要一个快速功能。我自己写的，但它似乎运行速度很慢：

// find string in "str", split at the position, delivers left and right side 

func revFindSplit_(str : String, searchString : String) -> (String, String) { 
    let strr = String(str.characters.reversed()) // reverse main string 
    let searchStringr = String(searchString.characters.reversed()) // reverse search string too 

    if let strrindex = strr.range(of: searchStringr) { // now we can search from back to front 

     let rangeOfS2 = strr.characters.startIndex..<strrindex.lowerBound // we got search result: part 1 (front) 
     let rangeOfS1 = strrindex.lowerBound..<strr.characters.endIndex // part 2 (back) 
     let S2 = String(strr[rangeOfS2].characters.reversed()) // put together and reverse again 
     let S1 = String(strr[rangeOfS1].characters.reversed()) 

     // here we have to remove search string 
     let S1M1 = String(S1.characters.prefix(S1.characters.count - searchString.characters.count)) 

     return (S1M1, S2) 
    } 
    else { 
     return (str, "") // without splitting 
    } 
} 

// split path of filename into all 3 part: directory name, filename without extension, extension (without dot) 
// in one call (faster than the 3 functions separatly) 
func splitFilename_(str: String) -> (directory: String, filenameOnly: String, ext: String) { 
    let url = NSURL(fileURLWithPath: str) 
    let path = url.path! 

    // split path and filename 
    let (directory, filenameExt) = revFindSplit_(str: path, searchString: "/") 
    // split filename in filenameOnly and extension 
    let (filenameOnly, ext) = revFindSplit_(str: filenameExt, searchString: ".") 

    return (directory, filenameOnly, ext) 
} 

有没有什么办法可以大大提高速度？ （可能使用库函数）

Answer 1

您可以减少整个代码：

func splitFilename(str: String) -> (directory: String, filenameOnly: String, ext: String) { 
    let url = URL(fileURLWithPath: str) 
    return (url.deletingLastPathComponent().path, url.deletingPathExtension().lastPathComponent, url.pathExtension) 
} 

Answer 2

按现代CPU标准划分数千个字符串并不是一项大任务。要让英特尔CPU陷入困境，您需要数百万美元。你确定这是你的应用程序的瓶颈吗？

“过早的优化是所有罪恶的根源” - 高德纳

最后，你的代码是史诗！你有没有尝试内置到NSString的路径操作？

func splitFileName(str: String) -> (directory: String, fileName: String, extension: String) { 
    let path = str as NSString 
    let directory = path.deletingLastPathComponent 

    let fileNameWithExtension = path.lastPathComponent as NSString 
    let fileNameWithoutExtension = fileNameWithExtension.deletingPathExtension 
    let fileExtension = fileNameWithExtension.pathExtension 

    return (directory, fileNameWithoutExtension, fileExtension) 
}