Decodes a value of the given type for the given key, if present.
Required. Default implementation provided.
- Xcode 10.0+
- Swift Standard Library
The type of value to decode.
The key that the decoded value is associated with.
A decoded value of the requested type, or
nil if the
Decoder does not have an entry associated with the given key, or if the value is a null value.
This method returns
nil if the container does not have a value associated with
key, or if the value is null. The difference between these states can be distinguished with a