ArrayHelpers.swift

extension Array {
    
    func first() -> Element? {
        if isEmpty {
            return nil
        }
        return self[0]
    }
    
    func last() -> Element? {
        if isEmpty {
            return nil
        }
        let index = count - 1
        return self[index]
    }
    
    func tail() -> T[] {
        if self.isEmpty || self.count == 1 {
            return Array()
        }
        
        return self.subArray(NSRangeFromString("{1, \(self.count - 1)"))
    }
	
    func subArray(range : NSRange) -> T[]{
        var newArray = Array()
		
        for i in range.location...range.length {
            newArray += self[i]
        }
		
        return newArray
    }
}

DispatchAfter.swift

let offset = 2.0
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(offset * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), {
    // Do something
})

Singleton.swift

class func sharedClient() -> CanaryClient {
    struct Static {
        static var instance: CanaryClient?
        static var token: dispatch_once_t = 0
    }
    dispatch_once(&Static.token, {
        Static.instance = CanaryClient()
    })
    return Static.instance!
}

Typedefs.swift

// You can make aliases for closure types
typealias AccountStoreMultipleAccountsCompletion = (ACAccount[]?, NSError?) -> ()
typealias AccountStoreSingleAccountCompletion = (ACAccount?, NSError?) -> ()