Update Root.Plist on Compile - ios

Question

I have an app settings file which displays the version number for our app. The idea is to update the Root.plist on compile so that we don't have to update two places rather than one. We update theBuild settings version and would like those settings to update the Root.plist on compile.
This code extracts the information for the build settings, how do I update the Root.plist file?
NSString *appBuildNo = [[NSBundle mainBundle]objectForInfoDictionaryKey:#"CFBundleShortVersionString"];
NSString *appBuildVersion = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"CFBundleVersion"];
NSString *appBuildStr = [NSString stringWithFormat:#"%# Build %#", appBuildNo, appBuildVersion];
NSURL * settingsURL = [[NSBundle bundleWithURL:[[NSBundle mainBundle] URLForResource:#"Settings" withExtension:#"bundle"]]
URLForResource:#"Root" withExtension:#"plist"];
NSDictionary * settingsDict = [NSDictionary dictionaryWithContentsOfURL:settingsURL];
NSArray * settingsArr = [settingsDict objectForKey:#"PreferenceSpecifiers"];
NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
for( NSDictionary * setting in settingsArr ){
NSString * key = [setting objectForKey:#"DefaultValue"];
[defaults setValue:appBuildStr forKey:key];
[defaults synchronize];
break;
}
The idea is that defaults updates Root.plist but it is not working. Any help would be appreciated

Answer 1

Droppy was very helpful in helping me to fix this. After setting up my Settings Bundle and the Root.plist file, I added the following code to my AppDelegate and called it from the didFinishLaunchingWithOptions.
- (void)updateVersionInfo
{
//This method updates the Root settings to display current Version and Build No in Settings Bundle
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *appVersionNumber = [[[NSBundle mainBundle] infoDictionary] objectForKey:#"CFBundleVersion"];
NSString *appBuildNo = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"CFBundleShortVersionString"];
NSString *versionNumberInSettings = [NSString stringWithFormat:#"%# Build %#", appBuildNo, appVersionNumber];
[defaults setObject:versionNumberInSettings forKey:#"version"];
}
This code then adds the contents of the Version in the info.plist file to my Settings Bundle.