Not able to write into text file

I need to write a string into a file. For that, my code is:

-(void)writeToFile:(NSString *)fileName: (NSString *)data {

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    // the path to write file
    NSString *appFile = [documentsDirectory stringByAppendingPathComponen开发者_如何学编程t:fileName];
    [data writeToFile:appFile atomically:YES];  
}

I am calling this method like this

ownServices *obj = [[ownServices alloc]init];
[obj writeToFile:@"iphone.txt" :@"this is mahesh babu"];

but it didn't write into the text file.

What's the reason? Can anyone please help me.

Thank u in advance.

The most likely problem is that the documents directory does not exist. Create it if it doesn't, then write to it:

NSArray *paths = NSSearchPathForDirectoriesInDomains(
        NSDocumentDirectory, NSUserDomainMask, YES);
NSString *parentDir = [paths objectAtIndex:0];

/* Create the parent directory.
 * This is expected to fail if the directory already exists. */
(void)[[NSFileManager defaultManager]
       createDirectoryAtPath:parentDir
       withIntermediateDirectories:YES
       attributes:nil error:NULL];
NSString *path = [parentDir stringByAppendingPathComponent:fileName];

/* Now write, and if it fails, you'll know why thanks to the |error| arg. */
NSError *error = nil;
BOOL ok = [data writeToFile:path options:NSDataWritingAtomic error:&error];
if (!ok) {
    NSLog(@"%s: Failed to write to %@: %@", __func__, path, error);
}

Even simpler would be to use the latest API, which will create the directory for you if it doesn't already exist:

NSError *error = nil;
NSURL *parentURL = [[NSFileManager defaultManager]
    URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask
    appropriateForURL:nil create:YES error:&error];
if (!parentURL) {
    NSLog(@"%s: *** Failed to get documents directory: %@", __func__, error):
    return;
}

NSURL *furl = [parentURL URLByAppendingPathComponent:fileName];
error = nil;
BOOL ok = [data writeToURL:furl options:NSDataWritingAtomic error:&error];
if (!ok) {
    NSLog(@"%s: *** Failed to write to %@: %@", __func__, furl, error);
}

Firstly, you are calling your method strangely. Rename the method to

-(void)writeString:(NSString *) data toFile:(NSString *)fileName

and call it like so:

[obj writeString:@"this is mahesh babu" toFile:@"iphone.txt"];

Secondly, writeToFile:atomically: is deprecated, use writeToFile:atomically:encoding:error::

NSError *error = nil;
BOOL success = [data writeToFile:appFile  atomically:YES encoding:NSUTF8Encoding error:&error];
if (!success) {
    NSLog(@"Error: %@", [error userInfo]);
}

This way, you also see what the error is.

Your code looks OK. Use the debugger (or an NSLog statement) to verify the values of data and appFile. If data is nil, nothing will happen (including no errors) because sending a message to nil is a no-op. It's also possible that appFile is not the path you think it is.

Check the permissions of the directory you are trying to write to (ls -la). On the device you can't, but on the simulator you can. Is it read-only for you? Is it owned by another user?

Assuming that isn't the problem, try calling with atomically:NO. Atomic file writing is performed by writing a file, then renaming it to replace the old one. If the problem is there, that will isolate the problem.

Bonus Style Critique

• Class names should start with an uppercase letter: OwnServices instead of ownServices
• Although your method name is perfectly valid, it's unusual to have two parameters with no words to separate them. A name like writeToFile:string: would be better.
• Don't name a variable data if it is meant to point to an instance of something other than NSData. It's confusing, and there's almost a better (more specific) word you can use beside "data".