Swift Ordered Dictionary

OrderedDictionary.swift

//
//  OrderedDictionary.swift
//  DMS
//
//  Created by Freddy on 12/12/14.
//  Copyright (c) 2014 DMSCompany. All rights reserved.
//

import Foundation

struct OrderedDictionary<Tk: Hashable, Tv>{
    var keys: Array<Tk> = []
    var values: Dictionary<Tk,Tv> = [:]
    
    init(){
        
    }
    
    subscript(key:Tk) -> Tv?{
        get{
            return self.values[key];
        }
        set(newValue){
            if (newValue == nil){
                self.values.removeValueForKey(key)
                self.keys.filter {$0 != key}
                return;
            }
            
            let oldValue = self.values.updateValue(newValue!, forKey: key);
            if oldValue == nil{
                self.keys.append(key);
            }
        }
    }
    
    func getPair(i: Int) -> (key: Tk, value: Tv)?{
            var key = self.keys[i];
            
            return (key, self.values[key]!);
    }
    
    
    
}

Why not just use an Array of tuples instead of an OrderedDictionary?

@mattdipasquale Then how would you get the value for a specific key (orderedDict["something"])?

@mattdipasquale I've done that in my own projects but it causes O(n) lookup times which can be easily avoided by using an actual dictionary.