pala

#import <Foundation/Foundation.h>

typedef void (^RCTaskBlock)(NSString *keyPath, id object, NSDictionary *change);

@interface TZReceptionist : NSObject
+ (id)receptionistForKeyPath:(NSString *)path
                      object:(id)obj
                       queue:(NSOperationQueue *)queue
                        task:(RCTaskBlock)task;
@end

pala

public class var sharedConfiguration: AppConfiguration {
    struct Singleton {
        static let sharedAppConfiguration = AppConfiguration()
    }

    return Singleton.sharedAppConfiguration
}

// Checkout Lister: A Productivity App Built in Swift by Apple

pala

// https://twitter.com/dwineman/status/601853359839006721
// Default arguments are expressions, not constants, evaluated only when necessary. 

extension UIImage {
    static func emptyImage(size: CGSize, scale: CGFloat = UIScreen.mainScreen().scale) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }