Saving NSDatePicker to a string and saving that to NSUserDefaults...

Question

Saving NSDatePicker to a string and saving that to NSUserDefaults I have it saved to a string then I have code that should save it to NSUSerDefaults so that when the program starts it is saved as the string not null. Here is the code [CODE]#import "MainView.h"
#import "DateView.h"
@implementation MainView
-(void)awakeFromNib
[self removeFromSuperview];
[self addSubview:dateView];
[dateView setdateandtime];
[dateView permsavedattime];
@end [/CODE] [CODE]#import "DateView.h"
#include "MainView.h"//Use #import this is to see if #include Works
@implementation DateView
-(IBAction)showuserdefaultdate
[self userdefaultdate];
//dateoutput.text =tddate;
-(void)permsavedattime
tddate=[prefs stringForKey:@"testing"];
tdtime=[prefs stringForKey:@"timetesting"];
dateoutput.text =[[NSString alloc] initWithFormat:@"%@",tddate];
-(void)userdefaultdate
prefs =[NSUserDefaults standardUserDefaults];
[prefs setInteger:tddate forKey:@"testing"];
[prefs setObject:tdtime forKey:@"timetesting"];
-(void)setdateandtime
[Today setDate:[NSDate date] animated:YES];
//formatting date style
dateformatter = [ [ NSDateFormatter alloc ] init ];
[ dateformatter setDateStyle:NSDateFormatterLongStyle];
[ dateformatter setTimeStyle:NSDateFormatterNoStyle ];//makes it so the time is not included
//[ formatter setTimeStyle:NSDateFormatterLongStyle ];//set to anystyle besides
//NoStyle if you dont want time included.
[Time setDate:[NSDate date] animated:YES];
//formatting date style
timeformatter = [ [ NSDateFormatter alloc ] init ];
[ timeformatter setDateStyle:NSDateFormatterNoStyle];//makes it so it doesn't get the date
[ timeformatter setTimeStyle:NSDateFormatterShortStyle];//makes it so the time is just hour and minute and A.M. or P.M.
//[ formatter setTimeStyle:NSDateFormatterLongStyle ];//set to anystyle besides
//NoStyle if you dont want time included.
-(IBAction)recieveDate
tddate= [dateformatter stringFromDate:Today.date];//Asigning the date to the string
dateoutput.text =tddate;
-(IBAction)recievetime
tdtime= [timeformatter stringFromDate:Time.date];//Asigning the date to the string
timeoutput.text =tdtime;
-(IBAction)canceltime
[Time setDate:[NSDate date] animated:YES];
tdtime= [timeformatter stringFromDate:Time.date];//Asigning the date to the string
timeoutput.text =tdtime;
-(IBAction)canceldate
[Today setDate:[NSDate date] animated:YES];
tddate= [dateformatter stringFromDate:Today.date];//Asigning the date to the string
dateoutput.text =tddate;
@end[/CODE] What am I missing? It keeps coming up Null I need it saved right so I can send it through email

Answer 1

softwarespecial wrote:
why can't I have the prefs saved in the .h
You can save that address in an ivar if you want to, but there's no purpose to that. The standardUserDefaults object is a +shared class object+. It's like a dictionary object that's maintained for your program by the NSUserPreferences class. You can read from or write to it at any time for the duration of your program. So whenever you get the shared object's address [NSUserDefaults standardUserDefaults], you're just getting the address of that same object each time.
In case the above doesn't make sense, I ran across a good explanation by Danneman in the last message on this page: [http://www.iphonedevsdk.com/forum/iphone-sdk-development/18716-set-settings-va riable-code.html].
When I did that as you so wisely pointed out it didn't work but when I saved it at each point I needed it it works.
When you change two things at once it's easy to forget the first and assume the second change solved the problem. Actually, I don't think saving prefs in your ivar had anything to do with your bug. What fixed it was getting a pointer to the shared std defaults object in this method:
-(void)permsavedattime
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; <-- get the shared object
tddate=[prefs stringForKey:@"testing"];
tdtime=[prefs stringForKey:@"timetesting"];
dateoutput.text =[[NSString alloc] initWithFormat:@"%@",tddate];
Without the first line of the above, I'm fairly sure that your prefs ivar was nil. I didn't see any code that initialized that ivar prior to the first time userdefaultdate ran. It looked to me like permsavedattime ran at start up, well before prefs was set in userdefaultdate. If you're interested in backtracking, restore the file to the way it was when you posted, then add a NSLog() like this:
-(void)permsavedattime
// NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; <-- get the shared object
NSLog(@"prefs=%@", prefs);
tddate=[prefs stringForKey:@"testing"];
tdtime=[prefs stringForKey:@"timetesting"];
dateoutput.text =[[NSString alloc] initWithFormat:@"%@",tddate];
I wish to save lets say five different things to NSUSerDefaults would I be able to do it all with my NSUserDefaults prefs or would I have to create a another one for some of them?
You know the answer to your second question now, right? The important point is that you're never creating the shared object, you're just asking for its address whenever you need it.
Btw, there's another user defaults method you should know about: The synchronize method writes the data to disk. You might want to do that when your app is ready to exit. E.g., in the app delegate:
- (void)applicationWillTerminate:(UIApplication *)application {
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[prefs synchronize];
Although the docs suggest synchronize when the app is about to exit, I'm not sure it's necessary. I think the system might write the defaults out to disk anyway when the app terminates, but not sure about this. +User Defaults Programming Topics for Cocoa+ says:
On Mac OS X v10.5 and later, in applications in which a run-loop is present, synchronize is automatically invoked at periodic intervals. Consequently, you might synchronize before exiting a process, but otherwise you shouldn’t need to.
The above is in the iPhone edition, so I think it applies.
It might also be a good idea to update the data and call resetStandardUserDefaults in didReceiveMemoryWarning. I'm not clear about the need for reset either though, since the system may do that for you as well. But on a memory warning, you would definitely want to update the user default data if some of it is stored in an object to be released. You can find out how your app behaves on a memory warning by selecting Hardware->Simulate Memory Warning from the iPhone Simulator menu.
- Ray