Write a file on iOS

Question

How do I write a file on iOS? I'm trying to do it with the following code but I'm doing something wrong:

char *saves = "abcd";
NSData *data = [[NSData alloc] initWithBytes:saves length:4]; 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"MyFile"];
[data writeToFile:appFile atomically:YES];

I have created MyFile.txt on resources.

Please describe exactly what is going wrong. – Shaggy Frog Apr 11 '11 at 10:17 — Shaggy Frog, Apr 11 '11 at 10:17

score 110 · Answer 1 · edited Jan 06 '18 at 19:38

110

May be this is useful to you.

//Method writes a string to a text file
-(void) writeToTextFile{
        //get the documents directory:
        NSArray *paths = NSSearchPathForDirectoriesInDomains
            (NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];

        //make a file name to write the data to using the documents directory:
        NSString *fileName = [NSString stringWithFormat:@"%@/textfile.txt", 
                                                      documentsDirectory];
        //create content - four lines of text
        NSString *content = @"One\nTwo\nThree\nFour\nFive";
        //save content to the documents directory
        [content writeToFile:fileName 
                         atomically:NO 
                               encoding:NSUTF8StringEncoding 
                                      error:nil];

}


//Method retrieves content from documents directory and
//displays it in an alert
-(void) displayContent{
        //get the documents directory:
        NSArray *paths = NSSearchPathForDirectoriesInDomains
                        (NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];

        //make a file name to write the data to using the documents directory:
        NSString *fileName = [NSString stringWithFormat:@"%@/textfile.txt", 
                                                      documentsDirectory];
        NSString *content = [[NSString alloc] initWithContentsOfFile:fileName
                                                      usedEncoding:nil
                                                             error:nil];
        //use simple alert from my library (see previous post for details)
        [ASFunctions alert:content];
        [content release];

}

edited Jan 06 '18 at 19:38

auspicious99

3,902
1
44
58

answered Apr 11 '11 at 10:09

Chetan Bhalara

10,326
6
32
51

1

I cannot find the file where i write it seems it doesnt exist – Riccardo Queri Apr 11 '11 at 10:18
You can change the document directory path. – Chetan Bhalara Apr 11 '11 at 10:29
use -- #define DOCUMENTS_FOLDER [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] – Chetan Bhalara Apr 11 '11 at 10:30
if i dont do this wich is the default directory for my files? – Riccardo Queri Apr 11 '11 at 10:34
dont forget the command [[NSUserDefaults standardUserDefaults] synchronize]; after save.. – Juan Munhoes Junior Feb 19 '13 at 19:12
@JuanMunhoesJunior : I have not used NSUseDefaults in this code, Then why I write it. – Chetan Bhalara Feb 20 '13 at 05:04
3

What is NSStringEncodingConversionAllowLossy? Should the encoding be: NSUTF8StringEncoding instead? – Ron Jun 10 '13 at 15:57
@Ron I made the edit, `NSUTF8StringEncoding` is required here. – Joshua Gross Oct 17 '13 at 22:47
@Ron Yes, with NSStringEncodingConversionAllowLossy, it gives a write error (these days with Xcode 9, iOS 11, etc.), the error being "The file couldn’t be saved using the specified text encoding." – auspicious99 Jan 06 '18 at 15:00

score 26 · Accepted Answer · edited Nov 17 '11 at 12:22

26

Your code is working at my end, i have just tested it. Where are you checking your changes? Use Documents directory path. To get path -

NSLog(@"%@",documentsDirectory);

and copy path from console and then open finder and press Cmd+shift+g and paste path here and then open your file

edited Nov 17 '11 at 12:22

dandan78

13,328
13
64
78

answered Apr 11 '11 at 10:16

saadnib

11,145
2
33
54

I guess this is where i'm wrong.. I have created MyFile inside my resource app directory.. Bu there arent changes there.. Where do I got to check or create the file? – Riccardo Queri Apr 11 '11 at 10:26

score 12 · Answer 3 · edited Nov 14 '16 at 08:59

Swift

func saveFile() {
    let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
    let documentsDirectory = paths[0] as! String
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content = "Hello World"
    content.writeToFile(fileName, atomically: false, encoding: NSUTF8StringEncoding, error: nil)
}

func loadFile() {
    let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
    let documentsDirectory = paths[0] as! String
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content: String = String(contentsOfFile: fileName, encoding: NSUTF8StringEncoding, error: nil)!
    println(content)
}

Swift 2

func saveFile() {
    let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
    let documentsDirectory = paths[0]
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content = "Hello World"
    do{
        try content.writeToFile(fileName, atomically: false, encoding: NSUTF8StringEncoding)
    }catch _ {

    }

}

func loadFile()->String {
    let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
    let documentsDirectory = paths[0] 
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content: String
    do{
       content = try String(contentsOfFile: fileName, encoding: NSUTF8StringEncoding)
    }catch _{
        content=""
    }
    return content;
}

Swift 3

func saveFile() {
    let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
    let documentsDirectory = paths[0]
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content = "Hello World"
    do{
        try content.write(toFile: fileName, atomically: false, encoding: String.Encoding.utf8)
    }catch _ {

    }

}

func loadFile()->String {
    let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
    let documentsDirectory = paths[0]
    let fileName = "\(documentsDirectory)/textFile.txt"
    let content: String
    do{
        content = try String(contentsOfFile: fileName, encoding: String.Encoding.utf8)
    } catch _{
        content=""
    }
    return content;
}

score 7 · Answer 4 · answered Apr 11 '11 at 10:13

7

Try making

NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"MyFile"];

as

NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"MyFile.txt"];

answered Apr 11 '11 at 10:13

visakh7

26,380
8
55
69

Write a file on iOS

4 Answers4

Linked