[swift-users] Dictionary with optional values

[Jordan Rose]

> On May 18, 2016, at 09:38, Ray Fix via swift-users <swift-users at swift.org> wrote:
> 
> 
>> 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.

There’s a bit more discussion of this on the Apple Swift blog: https://developer.apple.com/swift/blog/?id=12 <https://developer.apple.com/swift/blog/?id=12>

Jordan

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