Application Settings
and User Defaults
- Parimal Satyal (realityequation.net)
October 28, 2009
Based on Chapter 10 ‘Application Settings and User Defaults’
Apress Beginning iPhone 3 Development: Exploring the iPhone SDK
by Dave Mark and Jeff LaMarch

Prefs
Most Mac apps have ‘Preferences’
Persistent Data/Settings
Settings app on iPhone OS
UI is built for you, uses plist

Settings
Apps can have own
tab in the Settings app
When in-app, when in
Settings app?
‘Backdoor’ prefs that
don’t need changing
Else, users must quit

UPrefs: Utility App

Utility App Goodness
Free UI
Free ‘flip side
view’ (animated)
Custom UIView
subclasses:
MainView
FlipsideView

Settings Bundle
‘Settings Bundle’ to provide the data
Each bundle must have Root.plist
Additional views through
additional plists as child views
in Root.plist

New File > Resource

Root.plist Format
Root node is always a dictionary
(so must have key and value)
Children nodes can be:
Dictionaries • capable of containing other data
Arrays • capable of containing other data
Boolean
Data
Number
String
StringsTable for localization; ignore

PreferenceSpecifiers

PreferenceSpecifiers

PreferenceSpecifiers
- Required: Type, Key, (Title)

PreferenceSpecifiers
Key
Key
- Required: Type, Key, (Title)
- Key vs Key: Confusing

Adding Stuff
and Grouping
Notice change in icons when expanded
PSGroupSpecifier signals new group
The contents of Root.plist determine
the UI and structure of Settings app

Other Inputs
Secure Text Field (isSecure key)
Multivalue field: PSMultiValueSpecifier
Array as child, with separate
Key list and Value list
Toggle Switch: PSToggleSwitchSpecifier
Slider: PSSliderSpecifier

Editing Root.plist

Editing Root.plist

Array to Drill Down

Magic of Root.plist
Open Root.plist
Spend some time playing around and
seeing what changes what
Add another control:
A Toggle, a Slider or just a Text Field

Getting Settings data
Easy, using the NSUserDefaults class
NSUserDefaults *defaults =
[NSUserDefaults standardUserDefaults];
defaultsbecomes a dictionary, so we can
do stuff like:
(NSString *) objectForKey:
(NSDate *) objectForKey:
(int) intForKey:
(BOOL) boolForKey:

UI: MainView.xib

MainViewController
Explore the .h and .m files
Take a look at these methods:
refreshFields:
flipSideViewControllerDidFinish:
viewDidAppear:
Declaring constants, creating a method
Property-ize and synthesize elements
Map them using NSUserDefaults class &
objectForKey: method

MainViewController.m
- (void) refreshFields {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
usernameLabel.text = [defaults objectForKey: kUsernameKey];
passwordLabel.text = [defaults objectForKey: kPasswordKey];
languageLabel.text = [defaults objectForKey: kLanguageKey];
beAwesomeLabel.text = [defaults objectForKey: kBeAwesomeKey];
awesomenessLabel.text = [[defaults objectForKey: kAwesomenessKey]
stringValue];
}
- (void) viewDidAppear:(BOOL)animated {
[self refreshFields];
[super viewDidAppear:animated];
}

MainViewController.m
- (void) refreshFields {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
usernameLabel.text = [defaults objectForKey: kUsernameKey];
passwordLabel.text = [defaults objectForKey: kPasswordKey];
languageLabel.text = [defaults objectForKey: kLanguageKey];
beAwesomeLabel.text = [defaults objectForKey: kBeAwesomeKey];
awesomenessLabel.text = [[defaults objectForKey: kAwesomenessKey]
stringValue]; ‹ don’t forget stringValue
}
- (void) viewDidAppear:(BOOL)animated {
[self refreshFields];
[super viewDidAppear:animated];
}

Changing Defaults
Design UI
Create outlets
Use getters and setters to make the
changes

FlipsideView.xib

Get what’s there when view loads
FlipsideViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
NSUserDefaults *defaults = [NSUserDefaults
standardUserDefaults];
awesomeSwitch.on = ([[defaults objectForKey:kBeAwesomeKey]
isEqualToString:@"Oui"]) ? YES: NO;
awesomenessSlider.value = [defaults
floatForKey:kAwesomenessKey];
}

Set new values when moving out
FlipsideViewController.m
- (void) viewWillDisappear:(BOOL)animated {
NSUserDefaults *defaults = [NSUserDefaults
standardUserDefaults];
NSString *prefValue = (awesomeSwitch.on)? @"Oui" :
@"Non";
[defaults setObject:prefValue forKey:kBeAwesomeKey];
[defaults setFloat:awesomenessSlider.value
forKey:kAwesomenessKey];
[super viewWillDisappear:animated];
}

Finishing Up
Clean up with dealloc, viewDidUnload for
both Views
Fix any Build errors
And you get...