Creating multiple themes in an iPhone App - ios

Question

I have recently released my first app to the App Store and still have a very long way to go with iOS development.
I'm looking to introduce themes into my app as an update so the user can select from 4-5 different themes.
I've got a tab bar controller and have set the 5th tab to be the "Settings" tab which contains a Table View with cells. The first cell contains the text "Themes" where the user can select it, be taken to a new Table view/Collection View to select the themes.
So I searched online and came across this incredible answer on doing just this:
How to create Multiple Themes/Skins for iphone apps?
Because I'm still new to development, I'm in need of assistance to take this forward.
To start off with, I have two themes:
1) DefaultTheme (Newiphonebackground.png)
2) PurplePinkTheme (Purplepinknew.png)
Following the instructions, I have created one plist for the Default theme and one plist for the PurplePink theme.
In the ThemeManager class that I created, I have:
- (id)init
{
if ((self = [super init]))
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *themeName = [defaults objectForKey:#"theme"] ?: #"DefaultTheme";
NSString *path = [[NSBundle mainBundle] pathForResource:themeName ofType:#"plist"];
self.styles = [NSDictionary dictionaryWithContentsOfFile:path];
}
return self;
}
+ (ThemeManager *)sharedManager
{
static ThemeManager *sharedManager = nil;
if (sharedManager == nil)
{
sharedManager = [[ThemeManager alloc] init];
}
return sharedManager;
}
In my table view, where the theme will get applied (it's going to get applied to every screen in the app but this is just to start off with where I'm testing with one scene in the app), in the viewDidLoad, I put:
NSDictionary *styles = [ThemeManager sharedManager].styles;
NSString *imageName = [styles objectForKey:#"DefaultTheme"];
UIImageView *backgroundImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]];
self.tableView.backgroundView = backgroundImageView;
That does nothing different because it applies the default theme. However if in the ThemeManager, I change the plist to be:
NSString *themeName = [defaults objectForKey:#"theme"] ?: #"PurplePinkTheme";
and in the viewDidLoad of the separate Table View, I set the code to be:
NSString *imageName = [styles objectForKey:#"PurplePinkTheme"];
Then upon loading my application, my PurplePinkTheme loads.
So far so good, but I don't think I've done anything substantial here.
I am confused from this point on. I am looking to start off with changing just the background images from the in-app settings and once I have that done, I'll look to change the custom navigation bars, etc.
So my questions are:
1) Why do I create one plist per theme?
2) How exactly do I link multiple plists in the ThemeManager class?
3) How do I link all of the themes up to the settings Theme cells allowing the user to choose?
I'm sorry this is vague, but I really need to understand how exactly I can carry on here. For example, I just don't get how to have multiple plists in the ThemeManager and how to move forward from here.
To recap, I, for now just want the ability to have multiple plist files with the different backgrounds, and for the user to go the settings tab in my app, click on the "Themes" cell and be able to select a different theme for the app without restarting the app.
I know the tutorial does carry on with explanations on that, but I'm just not quite sure I understand it all.
Any guidance on this would be massively appreciated.
Many thanks,

Answer 1

Your question is super long so I must confess I did not read the whole thing. That said I spent a lot of time with themes and the best solution I have found is to create an object that handles formatting. This is how I think you can implement it:
Create a formatter object extending NSObject
Have a property for each changeable piece of the theme:
for example if the background changes images you can have a UIImage in there called background. If the font color changes you have a UIFont property in there.
create a shared instance of your formater by adding:
+(Formater *) sharedInstance; //add to .h
+ (Formater *) sharedInstance //add to .m
{
if (!_sharedInstance)
{
_sharedInstance = [[Formater alloc] init];
}
}
Now in your view controller all you need to do is create a reference to your shared item and use that to style your view controller. (remember to make the changes in viewWillAppear not or it will not change after the setting is changed.
Voila!