Chapter9: application preferences question

Brabbeldas · February 22nd, 2012, 09:06 AM

When working my way through chapter 9 I run into a number of things I found a little funny.

First thing I noticed:
The book lets you start with adding the Settings.bundle file and lets you modify the Root.plist file. One of the things you do here is adding an item of type PSMultiValueSpecifier called 'Favorite Color'. Here you specify three colors (page 206/207).

Later you are asked to change the viewDidLoad method (page 211/212). Here you create and fill an array which will be used to fill the PickerView.
Should the PickerView not be filled with the items/colors we have just added to the Root.plist file?

Second thing I noticed(and this was a little weird to me):
At page 214 the book lets you change the application:didFinishLaunchingWithOptions: method. It lets you initialize the settings, which otherwise will be nil, and lets you set the default values..
Have we not already initialized the settings, and set their default values, inside the Root.plist file?

dparsons · February 23rd, 2012, 06:55 PM

Hello Brabbeldas,
From page 216 of the book:

Quote:

When your application runs for the first time, you need to set the values of the settings before you can use them. Hence, the best place to initialize them is in the application delegate.

This could of been explained a bit more but the reason that you created the array, set the values, and so on is because the values are nil the first time you run your application if the user hasn't run the settings app prior to the first run of the app itself.

That is why you do tests like this:

Code:

if (![defaults objectForKey:@âlogin_nameâ])
     [defaults setObject:@âlogin nameâ forKey:@âlogin_nameâ];

So if the value for login_name is nil we need to set the value.

hth.
-Doug

Brabbeldas · February 24th, 2012, 03:49 AM

Hi Doug, thanks for replying.

On the internet I indeed found the same thing you say:

Quote:

âthe values are nil the first time you run your application if the user hasn't run the settings app prior to the first run of the app itselfâ

I find that a little strange but if that is the way it works.. oke.

If an app has a large number of Application Preferences its not that efficient to check and set them one by one. I have found a pice of code which does all that for you: It loads the default values from all the AppPreferences within the Root.plist

Code:

Code:

- (void)registerDefaultsFromSettingsBundle {
    // Find the Settings.bundle //
    NSString *settingsBundle = [[NSBundle mainBundle] pathForResource:@"Settings" ofType:@"bundle"];
    if(!settingsBundle) {
        NSLog(@"Could not find Settings.bundle");
        return;
    }
    // Load the Root.plist into a Dictionary //
    NSDictionary *settings = [NSDictionary dictionaryWithContentsOfFile:[settingsBundle stringByAppendingPathComponent:@"Root.plist"]];
    // Load the PreferenceSpecifiers entry into an Array //
    NSArray *preferences = [settings objectForKey:@"PreferenceSpecifiers"];
    
    // Create a new Dictionary which will contain all AppPreferences with their Defaut value //
    NSMutableDictionary *defaultsToRegister = [[NSMutableDictionary alloc] initWithCapacity:[preferences count]];
    // Walk through all AppPrefrences loaded from the Root.plist //
    for(NSDictionary *prefSpecification in preferences) {
        // Get the 'Key' item from then specific AppPreference //
        NSString *key = [prefSpecification objectForKey:@"Key"];
        if(key) {
            // Add it to the defaultsToRegister Dictionary with its Default value //
            [defaultsToRegister setObject:[prefSpecification objectForKey:@"DefaultValue"] forKey:key];
        }
    }
    // Load the defaultsToRegister Dictionary into the UserDefaults class //
    [[NSUserDefaults standardUserDefaults] registerDefaults:defaultsToRegister];
}

Just call it once, only if the defaults have not been loaded yet:

Code:

 // Initialize the settings value first //
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if(![defaults objectForKey:@"login_name"])
        [self registerDefaultsFromSettingsBundle];

I hope this helps someone.