Playing around with Swift to implement a Queue that can take any object type

gistfile1.swift

class Queue {
    var items: Array<AnyObject> = []
    
    // Add an object to the tail of the queue
    func enqueue(object: AnyObject) {
        items += object;
    }
    
    // Remove the head of the queue and return the object
    func dequeue() -> AnyObject? {
        assert(items.count > 0, "Array has no items to dequeue")
        let object : AnyObject? = items[0]
        items.removeAtIndex(0)
        return object
    }
    
    // Empty the entire queue
    func clear() {
        items.removeAll(keepCapacity: false)
    }
    
    // Return if the queue is empty
    func empty() -> Bool {
        return items.count == 0
    }
    
    // Implement the subscript to peek at any index using queue[1] notation
    subscript(index: Int) -> AnyObject? {
        assert(index < items.count, "Index is out of bounds")
        return items[index];
    }
    
    // Return the object at the index a wrapper for using subscript notation
    func peek(index: Int) -> AnyObject {
        return items[index]
    }
    
    // Return the object at the front of the queue without mutation
    func peekHead() -> AnyObject {
        return items[0]
    }
    
    // Return the object at the end of the queue without mutation
    func peekTail() -> AnyObject {
        let index = items.endIndex - 1
        return items[index]
    }
}