How to read/write file with iOS, in simulator as well as on device?

Question

As I need to read a file when my app is launched and write it sometimes while using it, I tried to reach it with :

NSString *dataFile = [[NSBundle mainBundle] pathForResource:@"data" ofType:@"txt"];
NSLog(@"%@",dataFile);

And the file, that should be in my project folder, is instead in the simulator folder :

2012-06-13 17:36:56.398 MyFileApp[610:15203] /Users/Rob/Library/Application Support/iPhone Simulator/5.1/Applications/1FFD4436-DCCA-4280-9E47-F6474BEE0183/MyFileApp.app/myFile.txt

So if I want to read/write it in using the simulator as well as the real device, what should I do ?

Thanks for your advices

Solution 1

To read the file from the bundle do the following

NSString *dataFile = [[NSBundle mainBundle] pathForResource:@"data" ofType:@"txt"];

To read it from your sandbox storage (documents)

NSString *docPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/YourFile.txt"];
NSString *dataFile = [NSString stringWithContentsOfFile:docPath 
                                           usedEncoding:NSUTF8StringEncoding 
                                                  error:NULL];

To write to document folder

NSString *docPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/YourFile.txt"];
[dataFile writeToFile:docPath 
          atomically:YES 
            encoding:NSUTF8StringEncoding 
               error:NULL];

Please note you will not be able to write the file in the bundle folder of your application

Solution 2

Here is what you need to write and read a file text:

Write a file:

-(void) writeStringToFile:(NSString *)aString{
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *fileName = @"textFile.txt";
    NSString *fileAtPath = [filePath stringByAppendingString:fileName];
    if (![[NSFileManager defaultManager] fileExistsAtPath:fileAtPath]) {
        [[NSFileManager defaultManager] createFileAtPath:fileAtPath contents:nil attributes:nil];
    }
    [[aString dataUsingEncoding:NSUTF8StringEncoding] writeToFile:fileAtPath atomically:NO];
}

and read a file:

-(NSString *)readStringFromFile{
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *fileName = @"textFile.txt";
    NSString *fileAtPath = [filePath stringByAppendingString:fileName];
    return [[NSString alloc] initWithData:[NSData dataWithContentsOfFile:fileAtPath] encoding:NSUTF8StringEncoding];
}

and finally I test my code at viewDidLoad:

    NSString *text = @"I'm an iOS developer and I'm living at HCM city";
    [self writeStringToFile:text];
    NSString *strResult = [self readStringFromFile];
    NSLog(@"%@", strResult);

Solution 3

For write files the methods are -[NSData writeToURL:atomically:] and -[NSString writeToURL:atomically:encoding:error:] can be used if you link to the Foundation framework.

For reading files the methods are -[NSData initWithContentsOfURL:options:error:] and -[NSString initWithContentsOfURL:encoding:error:].

Comments

[Rob]

If I use a file from my documents folder it will work with the simulator, but when I use my app on a device, what to do ? Use the bundle folder ?

[Rob]

Right, I see what you do using NSHomeDirectory. Thanks a lot !

[Rob]

I just need a last information. I have a folder called myFileApp, containing some folders (and another folder myFileApp), this one contains my .m/.h docs and my data file. What's the path I have to use in stringByAppendingPathComponent with this config ?

[Omar Abdelhafith]

If this is inside your bundle then use the first line i added, to load it from bundle resources :)

[Rob]

Well I see... so in fact, when the app launches, I have to read my bundle's file, then copy it in the sandbox, and make all the edits here ? And if I finally want to replace the bundle's file with the sandbox's one when exiting the app? I'm sorry but it's a little hard to understand..