How to write a String in different lines to a .txt file on iOS - ios

Question

I am trying to write a string to a t.t file in the documents folder of my app. I can write the string to it, but when I write another string to the file it overwrites the other string, is it possible to write more strings to a text files, with a blank line between strings, many in this formate
String
String
Strine
…
I am using this code to write the string to an text file, it works for one string, but not for multible strings.
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:#"%#/Barcodedata.txt",
documentsDirectory];
//create content - four lines of text
NSString *content = [NSString stringWithFormat:#"%#",sym.data];
//save content to the documents directory
[content writeToFile:fileName
atomically:NO
encoding:NSStringEncodingConversionAllowLossy
error:nil];

Answer 1

There's a few ways to do this, depending on how you implemented your code.
One way would be to load up the original .txt file into a NSMutableString object and then append that new line to the end of the string and re-write out the file (this isn't super efficient, especially as you start appending after 1000 strings, 100 strings, 50 strings, etc.)
Or you could use the low level C function "fwrite" with the append bit set.
Edited:
Since you want to see code, here's how to do it with my first suggestion:
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:#"%#/Barcodedata.txt", documentsDirectory];
//create content - four lines of text
NSError * error = NULL;
NSStringEncoding encoding;
NSMutableString * content = [[NSMutableString alloc] initWithContentsOfFile: fileName usedEncoding: &encoding error: &error];
if(content == NULL)
{
// if the file doesn't exist yet, we create a mutable string
content = [[NSMutableString alloc] init];
}
if(content)
{
[content appendFormat: #"%#", sym.data];
//save content to the documents directory
BOOL success = [content writeToFile:fileName
atomically:NO
encoding:NSStringEncodingConversionAllowLossy
error:&error];
if(success == NO)
{
NSLog( #"couldn't write out file to %#, error is %#", fileName, [error localizedDescription]);
}
}