iOS change UIViewController

Question

In my app I have a gradient as a background. This gradient is made programmatically. The way that I now use this is like this:

I have a UIViewController which needs to display the gradient and in that class I do this :

- (void) viewWillAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    [Gradient gradientInViewController:self];
}

This ain't so bad but this needs to be done in all the classes which isn't very good programming. What I want is instead of making a class a UIViewController, I want it to be a GradientViewController which is a subclass of UIViewController and in this class I will handle everything.

So my question is how do I do this? I think this has to be done through categories? But I can't figure out how to get the image on the screen. Should this be done in viewWillAppear or something?

simply change [super viewDidAppear:animated]; to [super viewDidAppear:animated]; — NANNAV
– NANNAV, Commented Oct 31, 2013 at 8:27
@NANNAV not sure what the difference is between them did you mean to say [super viewWillAppea:animated]; — Popeye
– Popeye, Commented Oct 31, 2013 at 8:31

jbat100 · Accepted Answer · 2013-10-31 08:28:46Z

2

Make a GradientViewController which handles the gradient drawing

@interface GradientViewController : UIViewController

@end

@implementation GradientViewController

- (void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [Gradient gradientInViewController:self];
}

@end

Then inherit all your other controllers from that

@interface YourViewController : GradientViewController

@end

@implementation YourViewController

- (void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    // no need to do anything
}

@end

It's more flexible to do it through helper classes or categories though, even if there's a bit of repetition.

Note as pointed out by Nguyen Duc, that you are calling [super viewDidAppear:] for viewWillAppear: which is wrong, I edited the answer.

edited Oct 31, 2013 at 8:28

answered Oct 31, 2013 at 8:22

jbat100

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1 Comment

Haagenti Over a year ago

I will give you the best answer since it gives an entire explanation! Thank you

zadr · Accepted Answer · 2013-10-31 08:23:44Z

1

Why not use Interface Builder and have a xib that knows how to load your image for you automatically?

answered Oct 31, 2013 at 8:23

zadr

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Comments

Echelon · Accepted Answer · 2013-10-31 08:29:13Z

You can get this behaviour "for free" throughout your app simply by subclassing UIViewController:-

@interface GradientViewController : UIViewController 
@end

and implementing your gradient code in viewDidLoad: as such:-

- (void)viewDidLoad
{
    [super viewDidLoad];
    [Gradient gradientInViewController:self];
}

Then just use GradientViewController instead of UIViewController everywhere you need your gradient.

Alternatively you can use a category. This can be useful because you can use categories for "themes" for your app, configuring various UI elements of your UIViewControllers. But I'd set up a category on UIViewController specifically to set your gradient, and then call the category method in every view controller that needs it - do not attempt to do it by overriding viewDidLoad: or viewWillAppear: in a category.

IluTov · Accepted Answer · 2013-10-31 09:01:31Z

0

Just create a new view controller (let's call it GradientViewController for example), put the same code that draws the gradient into its view viewWillAppear, then make all your view controllers a subclass of the view controller by replacing

@interface SomeViewController : UIViewController

with

@interface SomeViewController : GradientViewController

edited Oct 31, 2013 at 9:01

IluTov

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answered Oct 31, 2013 at 8:20

Hesham

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1 Comment

Haagenti Over a year ago

Thank you! Just realized I completely overthought this!

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