title: How to insert values into a nested Swift Dictionary
body: <p>I'm trying to insert new key-value pair in dictionary, which nested in another one <code>Dictionary</code>:</p>
  
  <pre><code>var dict = Dictionary&lt;Int, Dictionary&lt;Int, String&gt;&gt;()
  
  dict.updateValue([1 : "one", 2: "two"], forKey: 1)
  dict[1]?[1] // {Some "one"}
  
  if var insideDic =  dict[1] {
      // it is a copy, so I can't insert pair this way:
      insideDic[3] = "three"
  }
  
  dict // still [1: [1: "one", 2: "two"]]
  
  dict[1]?[3] = "three" // Cannot assign to the result of this expression
  dict[1]?.updateValue("three", forKey: 3) // Could not find a member "updateValue"
  </code></pre>
  
  <p>I believe should be a simple way to handle it, but I spent an hour and still can't figure it out. 
  I can use <code>NSDictionary</code> instead, but I really like to understand how I should manage nested <code>Dictionaries</code> in Swift?</p>