Simple way to read local file using Swift?

Question

I'm trying to learn the new Swift programming language. It looks great, but I'm having a difficult time doing something as simple as reading the content of a local .txt file.

I have tried the few examples I could find through Google, but they give compile errors, like this answer here: Read and write data from text file If I tweak the code a bit, it works, but can only read from a special location within the project.

Why isn't it just as simple to read a .txt file with Swift as it is with for instance Ruby? And how would I go about reading the content of a file located at ~/file.txt?

Thnx

Atomix · Accepted Answer · 2015-09-21T15:47:24.607

37

If you have a tilde in your path you can try this:

let location = "~/file.txt".stringByExpandingTildeInPath
let fileContent = NSString(contentsOfFile: location, encoding: NSUTF8StringEncoding, error: nil)

otherwise just use this:

let location = "/Users/you/Desktop/test.txt"
let fileContent = NSString(contentsOfFile: location, encoding: NSUTF8StringEncoding, error: nil)

This gives you a string representation of the file, which I assumed is what you want. You can use NSData(contentsOfFile: location) to get a binary representation, but you would normally do that for, say, music files and not a text file.

Update: With Xcode 7 and Swift 2 this doesn't work anymore. You can now use

let location = NSString(string:"~/file.txt").stringByExpandingTildeInPath
let fileContent = try? NSString(contentsOfFile: location, encoding: NSUTF8StringEncoding)

edited Sep 21 '15 at 15:47

answered Sep 15 '14 at 11:38

Atomix

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I got this error: `Cannot invoke initializer for type 'NSString' with an argument list of type '(contentsOfFile: String, encoding: Ulnt, error: NilLiteralConvertible)' – O.rka Sep 21 '15 at 00:44
let location = NSString(string:"/Users/you/Desktop/myCSVfile.csv") let fileContent = try? NSString(contentsOfFile: location as String, encoding: NSUTF8StringEncoding) – Naishta Dec 26 '15 at 11:02

score 15 · Answer 2 · edited Mar 07 '15 at 13:26

15

This would work:

let path = "~/file.txt"
let expandedPath = path.stringByExpandingTildeInPath
let data: NSData? = NSData(contentsOfFile: expandedPath)

if let fileData = data {
    let content = NSString(data: fileData, encoding:NSUTF8StringEncoding) as String
}

Note that data may be nil, so you should check for that.

EDIT: Don't forget conditional unwrapping - looks much nicer ;)

edited Mar 07 '15 at 13:26

borchero

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answered Sep 15 '14 at 11:45

Grimxn

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I don't get the "if let fileData = data" part? What is going on here? – O.rka Sep 21 '15 at 01:00
4

`data` is an optional. It's declared as one on the line above. To quote from "A Swift Tour", the first chapter of the book: "You can use if and let together to work with values that might be missing. These values are represented as optionals. An optional value either contains a value or contains nil to indicate that a value is missing. Write a question mark (?) after the type of a value to mark the value as optional." – Grimxn Sep 21 '15 at 07:24

Amirhossein72 · Answer 3 · 2019-12-08T18:26:14.450

12

    let file = "/Users/user/Documents/text.txt"
    let path=URL(fileURLWithPath: file)
    let text=try? String(contentsOf: path)

edited Dec 08 '19 at 18:26

answered May 13 '17 at 15:03

Amirhossein72

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5
7

1

This deserves way more +1. simple, clean, and no need for NS. Am I missing something? Someone enlighten me if this is flawed? – rayepps Dec 05 '19 at 09:11

score 3 · Answer 4 · answered Dec 28 '15 at 06:52

3

Relative path tip:

Instead of doing this:
NSString("~/file.txt").stringByExpandingTildeInPath

You can do this:
"\(NSHomeDirectory())/file.txt"

answered Dec 28 '15 at 06:52

Sentry.co

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score 2 · Answer 5 · answered Jul 02 '15 at 18:20

You may find this tool useful to not only read from file in Swift but also parse it simultaneously: https://github.com/shoumikhin/StreamScanner

Just specify the file path and data delimiters like this (see readme for more options):

import StreamScanner

if let input = NSFileHandle(forReadingAtPath: "/file/path")
{
     let scanner = StreamScanner(source: input, delimiters: NSCharacterSet(charactersInString: ":\n"))  //separate data by colons and newlines

     while let field: String = scanner.read()
     {
        //use field
     }
}

Hope, this helps.

score 1 · Answer 6 · answered Dec 26 '15 at 11:05

1

This worked for me in Swift 2.1, XCode7 to get the location and print the contents of CSV. ( you can create a simple CSV in Text Wrangler)

override func viewDidLoad() {
    super.viewDidLoad()

    let location = NSString(string:"/Users/*Myusername*/Documents/myCSVfile.csv")
    let fileContent = try? NSString(contentsOfFile: location as String, encoding: NSUTF8StringEncoding)
    print(fileContent)

}

answered Dec 26 '15 at 11:05

Naishta

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I haven't tested the code but thanks, this helped me decide where to read files directly after starting the app. – Neph Jun 18 '19 at 11:04

score 0 · Answer 7 · answered Nov 06 '17 at 07:48

0

Using the answer by Atomix, this will work in Swift 4:

let location = NSString(string: "~/test.txt").expandingTildeInPath    
let fileContent = try? NSString(contentsOfFile: location, encoding: String.Encoding.utf8.rawValue)

answered Nov 06 '17 at 07:48

NeRa

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score 0 · Answer 8 · answered Nov 24 '19 at 15:49

Swift 4:

 let filePath = "/Users/UserName/Desktop/FolderName/FileName.txt"
 let fullPath = NSString(string: filePath).expandingTildeInPath
 do
 {
     let fileContent = try NSString(contentsOfFile: fullPath, encoding: String.Encoding.utf8.rawValue)
     print(fileContent)
 }
 catch
 {
     print(error)
 }

Simple way to read local file using Swift?

8 Answers8

Relative path tip:

Linked

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