NSUserDefaults doubts - iphone

Question

#pragma mark SA_OAuthTwitterControllerDelegate
- (void) OAuthTwitterController: (SA_OAuthTwitterController *) controller authenticatedWithUsername: (NSString *) username {
NSLog(#"Authenicated for %#", username);
[_btnTwitter setTitle:username forState:UIControlStateNormal];
}
I have this code for displaying username for twitter ,and it works well,but when i navigate to another page and came back the title username of the button disappears,i know we have to set a NSUserDefault value in viewwillapper for checking the username exists or not.But i didn't know how to handle the nSUserDefault,if anyone have an idea to solve this issue please help me.
Thanks in advance.
EDIT:
- (void)viewWillAppear:(BOOL)animated{
//Sets up the NSUserDefaults
//Sets up the NSUserDefaults
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
//Checks if there is a saved User Name
if([defaults objectForKey:#"kTwitterUserName"])
NSString *username = [defaults objectForKey:#"kTwitterUserName"];
[_btnTwitter setTitle:username forState:UIControlStateNormal];
else
{
}
this is how my viewwillappear lokks
and
- (void) OAuthTwitterController: (SA_OAuthTwitterController *) controller authenticatedWithUsername: (NSString *) username {
NSLog(#"Authenicated for %#", username);
[_btnTwitter setTitle:username forState:UIControlStateNormal];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:username forKey:#"kTwitterUserName"];
[defaults synchronize];
}
this is how my twitermethod looks like

Answer 1

NSUserDefaults are very simple to work with. They are kind of like a dictionary, you set an object and a key. So to do what your trying to do, you can use something like the following:
//This just sets up the defaults - similar to allocating a dictionary
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
Then to set an object in your defaults, you set an object/key pair like this:
[defaults setObject:username forKey:#"kTwitterUserName"];
It is important to call this method at some point: [defaults synchronize];. This explicitly saves the defaults. So you might as well do it immediately after you set the username key.
Then to read the saved username:
NSString *username = [defaults objectForKey:#"kTwitterUserName"];
Your oAuth Method should look like this:
- (void) OAuthTwitterController: (SA_OAuthTwitterController *) controller authenticatedWithUsername: (NSString *) username {
//Any thing else you want to do - NSLogs, etc.
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:username forKey:#"kTwitterUserName"];
[defaults synchronize];
}
So your viewWillAppear will look something like this:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
//Sets up the NSUserDefaults
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
//Checks if there is a saved User Name
if([defaults objectForKey:#"kTwitterUserName"]) {
NSString *username = [defaults objectForKey:#"kTwitterUserName"];
} else
//Do something else because there is no saved username
NSLog(#"no username saved");
}
Let me know in a comment if you need any clarification.

Answer 2

You're correct in the aspect you'll want to save this somehow, and NSUserDefaults will work fine for this. Save and read samples are below:
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
// saving an NSString
[prefs setObject:#"username" forKey:#"UsersUsername"];
// reading an NSString
NSString *theString = [prefs stringForKey:#"UsersUsername"];

Answer 3

http://www.icodeblog.com/2008/10/03/iphone-programming-tutorial-savingretrieving-data-using-nsuserdefaults/ for more details