Check out example codes for "get files with file type swift". It will help you in understanding the concepts better.

Code Example 1

let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
let url = URL(fileURLWithPath: documentsPath)

let fileManager = FileManager.default
let enumerator: FileManager.DirectoryEnumerator = fileManager.enumerator(atPath: url.path)!
while let element = enumerator.nextObject() as? String, element.hasSuffix(".txt") {
    // do something


Code Example 2

let enumerator = FileManager.default.enumerator(atPath: folderPath)
let filePaths = enumerator?.allObjects as! [String]
let txtFilePaths = filePaths.filter{$0.contains(".txt")}
for txtFilePath in txtFilePaths{
    //Here you get each text file path present in folder
    //Perform any operation you want by using its path

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