Question

Can someone explain and give example code to do the following steps in my iPad app:

1. do some things in my app, which generates some data (as a string)
2. write that data to a text file
3. be able to plug in my iPad to my computer and grab those text files off

How can I do this?

Answer 1

For writing string in a file use this

NSString *str = @"your string";
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
NSString* filePath = [documentsDirectory stringByAppendingPathComponent:@"data.txt"];
NSError *error;
[str writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];

Then set Application supports iTunes file sharing key to YES in your plist file.

When you connect your device with iTunes from there you can save your data.txt
Here is the video how to get files from iTunes

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Edited as requested.

NSUserDefaults *deflt = [NSUserDefaults standardUserDefaults];
//this number file is saved, I'm not saving the file name as data0.txt.
//The first file to be saved is data1.txt
int num = [deflt integerForKey:@"fileNameNum"]; 
num++;
NSString *fileName = [NSString stringWithFormat:@"data%d.txt",num];;
NSString *str = @"your string";
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
NSString* filePath = [documentsDirectory stringByAppendingPathComponent:fileName];
NSError *error = nil;
[str writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
if (error == nil) {
    //Save the number of the file that you have save in doc directory
    [deflt setInteger:num forKey:@"fileNameNum"];
}