appearanceWhenContainedIn in Swift

Question

Update for iOS 9:

If you're targeting iOS 9+ (as of Xcode 7 b1), there is a new method in the UIAppearance protocol which does not use varargs:

static func appearanceWhenContainedInInstancesOfClasses(containerTypes: [AnyObject.Type]) -> Self

Which can be used like so:

UITextField.appearanceWhenContainedInInstancesOfClasses([MyViewController.self]).keyboardAppearance = .Light

If you still need to support iOS 8 or earlier, use the following original answer to this question.

For iOS 8 & 7:

These methods are not available to Swift because Obj-C varargs methods are not compatible with Swift (see http://www.openradar.me/17302764).

I wrote a non-variadic workaround which works in Swift (I repeated the same method for UIBarItem, which doesn't descend from UIView):

// UIAppearance+Swift.h
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface UIView (UIViewAppearance_Swift)
// appearanceWhenContainedIn: is not available in Swift. This fixes that.
+ (instancetype)my_appearanceWhenContainedIn:(Class<UIAppearanceContainer>)containerClass;
@end
NS_ASSUME_NONNULL_END

—

// UIAppearance+Swift.m
#import "UIAppearance+Swift.h"
@implementation UIView (UIViewAppearance_Swift)
+ (instancetype)my_appearanceWhenContainedIn:(Class<UIAppearanceContainer>)containerClass {
    return [self appearanceWhenContainedIn:containerClass, nil];
}
@end

Just be sure to #import "UIAppearance+Swift.h" in your bridging header.

Then, to call from Swift (for example):

# Swift 2.x:
UITextField.my_appearanceWhenContainedIn(MyViewController.self).keyboardAppearance = .Light

# Swift 3.x:
UITextField.my_appearanceWhenContained(in: MyViewController.self).keyboardAppearance = .light

ios 10 swift 3

UIBarButtonItem.appearance(whenContainedInInstancesOf: [UISearchBar.self]).title = "Kapat"

For iOS 8 & 7:

I use a category based on Alex's answer to specify multiple containers. This is a workaround until Apple officially supports appearanceWhenContainedIn in Swift.

UIAppearance+Swift.h

@interface UIView (UIAppearance_Swift)
/// @param containers An array of Class<UIAppearanceContainer>
+ (instancetype)appearanceWhenContainedWithin: (NSArray *)containers;
@end

UIAppearance+Swift.m

@implementation UIView (UIAppearance_Swift)

+ (instancetype)appearanceWhenContainedWithin: (NSArray *)containers
{
    NSUInteger count = containers.count;
    NSAssert(count <= 10, @"The count of containers greater than 10 is not supported.");
    
    return [self appearanceWhenContainedIn:
            count > 0 ? containers[0] : nil,
            count > 1 ? containers[1] : nil,
            count > 2 ? containers[2] : nil,
            count > 3 ? containers[3] : nil,
            count > 4 ? containers[4] : nil,
            count > 5 ? containers[5] : nil,
            count > 6 ? containers[6] : nil,
            count > 7 ? containers[7] : nil,
            count > 8 ? containers[8] : nil,
            count > 9 ? containers[9] : nil,
            nil];
}
@end

Then add #import "UIAppearance+Swift.h" to your bridging header.

To use from Swift:

TextField.appearanceWhenContainedWithin([MyViewController.self, TableViewController.self]).keyboardAppearance = .Light

It was good if I could find a way using CVarArgType, but I found no clean solution.

Here's a less ugly, but still ugly, workaround inspired by @tdun.

1. Create a class to hold your Objective-C appearance. For the purposes of this example, let's call it AppearanceBridger.
2. Add this class to your bridging header. If you don't have a bridging header, create one.
3. Create a class method in AppearanceBridger named +(void)setAppearance and put the Objective-C appearance code in this method. For example:

+ (void)setAppearance {
    [[UIView appearanceWhenContainedIn:[UITableViewHeaderFooterView class], nil] setBackgroundColor:[UIColor whiteColor]];
}

4. In your Swift code where you set the appearance, call AppearanceBridger.setAppearance() and you should be good to go!

Hope this works well for people who see it.

Here's an ugly workaround solution I used....

Just make an Objective-C Cocoa Touch Class (UIViewController), named whatever you want.

I named mine WorkaroundViewController...

Now in (WorkaroundViewController.m):

-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

Run the Objective-C appearance code for .appearanceWhenContainedIn() (here's my example):

[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setDefaultTextAttributes:@{NSFontAttributeName: [UIFont fontWithName:@"Avenir-Light" size:16.0f]}];

Then create a bridging header for your Swift project and then initialize your Objective-C ViewController in your Swift code, like this (again, just my example):

var work : WorkaroundViewController = WorkaroundViewController()

Then you're done! Let me know if it works for you... Like I said, it's ugly, but works!

This can be extended to any class that conforms to the UIAppearance protocol -- not just UIViews. So here's a more generic version:

UIAppearance+Swift.h

#import <UIKit/UIKit.h>

@interface NSObject (UIAppearance_Swift)

+ (instancetype)appearanceWhenContainedWithin:(Class<UIAppearanceContainer>)containerClass;

@end

UIAppearance+Swift.m

#import "UIAppearance+Swift.h"

@implementation NSObject (UIAppearance_Swift)

+ (instancetype)appearanceWhenContainedWithin:(Class<UIAppearanceContainer>)containerClass {
    if ([self conformsToProtocol:@protocol(UIAppearance)]) {
        return [(id<UIAppearance>)self appearanceWhenContainedIn:containerClass, nil];
    }
    return nil;
}

@end