How To Down and store the Text File on Local Cache - ios

Question

I am developing an IOS app..Download data From URL and save on local cache..but i am using this code..first time data can stored in Local cache and also read on the text field..but Delete the app on simulator and run the and again store the text file on local cache..file can't be store..Any help or advice is greatly appreciated. thanks in advance.
NSURL *url = [NSURL URLWithString:#"http://webapp.opaxweb.net/books/"];
NSData *data_file = [[NSData alloc]initWithContentsOfURL:url];
NSString *resourceDocPath = [[NSString alloc] initWithString:[[[[NSBundle mainBundle] resourcePath] stringByDeletingLastPathComponent]stringByAppendingPathComponent:#"Documents"]];
NSString *filepath = [resourceDocPath stringByAppendingPathComponent:#"gurugranthsahib.txt"];
[data_file writeToFile:filepath atomically:YES];
NSLog(#"%#",filepath);
NSString* content = [NSString stringWithContentsOfFile:filepath
encoding:NSUTF8StringEncoding
error:NULL];

Answer 1

iOS does not allow writing to the app bundle.
Generally data is written to the Documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths firstObject];
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:fileName];
Note:
It is much better practice to use a method call that has an error parameter so when there is an error the error can be examined. In this case you could use:
NSError *error;
BOOL status = [string writeToFile:filePath options:NSDataWritingAtomic error:&error];
if (status == NO) {
NSLog(#"error: %#", error)
}