Check out example codes for "obj c write file". It will help you in understanding the concepts better.

Code Example 1

//writes an textfile to an place in the document directory
-(void)write:(NSString *)dir file:(NSString *)ff{
    //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:[@"%@/" stringByAppendingString:dir], 
                          documentsDirectory];
    //creates the content
    NSString *content = ff;
    //save content to the documents directory
    [content writeToFile:fileName 
              atomically:NO 
                encoding:NSStringEncodingConversionAllowLossy 
                   error:nil];
    
}


//usage: [self write:@"text.txt" file:@"this text will be saved"];

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