[swift-users] Dictionary with optional values

[Ray Fix]

> On May 18, 2016, at 3:56 AM, Artyom Goncharov via swift-users <swift-users at swift.org> wrote:
> 
> var noOptDict = ["one": 1, "two": 2, "three": 3 ]
> noOptDict["one"] = nil

Wow, interesting.  To me this was surprising behavior too.

The comment for Dictionary subscript  says:

    /// Access the value associated with the given key.
    ///
    /// Reading a key that is not present in `self` yields `nil`.
    /// Writing `nil` as the value for a given key erases that key from
    /// `self`.

Which is exactly what it is doing.  As the Zhaoxin said, you can use updateValue (and removeValueForKey) to get better results when dealing with optional dictionary values.

Ray